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The Trapp family patriarch made his name as the Austro-Hungarian Empire’s leading U-boat ace during World War I.

We know him best as the stern widower father of the Trapp Family Singers, a former Austrian naval officer who raises his children with strict military discipline. Captain Georg von Trapp is soon called upon to serve the German Kriegsmarine, but he and his family manage to flee Austria to avoid the coming Nazi darkness.

There are certainly elements of truth in The Sound of Music, but also a good measure of Hollywood license. Trapp was not the hard-nosed disciplinarian of the movie. He did use a whistle to summon his children—but only because the Trapp estate was so large and the children so plentiful. He was indeed a former naval officer who spent much of his life in the service of the Austro-Hungarian Empire, which collapsed in 1918 under the weight of its defeat in World War I. However, Trapp was not just any naval officer; he was an exceptional U-boat commander who sank more Allied tonnage than any other Austrian submarine captain.

Georg Ritter von Trapp was born in Zara (now Zadar in Croatia) on April 4, 1880. His father, August, an Austro-Hungarian naval officer, died from typhoid fever four years later. The younger Trapp attended the empire’s naval academy at Fiume, which supplied about half the navy’s officers. During the Boxer Rebellion in 1900, Sea Cadet 2nd Class Trapp led a telegraph and signal unit of eight men that was part of the landing detachment assigned to take the Taku forts on China’s Hai River.

He received his commission in 1908 and, while studying torpedo and submarine construction at the Whitehead factory at Fiume, met his future wife, Agathe Whitehead. She was the granddaughter of the wealthy industrialist Robert Whitehead, whose work with self-propelled torpedoes transformed naval warfare. They married on January 10, 1911, eventually producing seven children. When World War I began, Trapp was still serving in the Austro-Hungarian navy.

The war at sea during WWI went much differently than expected. Instead of engaging in immediate, apocalyptic clashes, the warring powers’ battleships spent the bulk of their time at their moorings, fulfilling the role of a “fleet in being.” The crews of smaller craft did most of the fighting—and dying—at sea. Submarines quickly took on a new role as commerce raiders, a function not generally considered before the war.

In 1914 Austria had about thirteen hundred miles of Adriatic seaboard, with another twenty-five hundred miles of island coastline. It had developed two important Adriatic naval bases, Pola and the Bocche di Cattaro. Italy’s refusal to enter the war on the side of the Central Powers, despite its pledge before the war to do so, destroyed the Austrian navy’s strategic position, forcing it to abandon most plans to operate beyond the Adriatic.

In April 1915, Lieutenant Commander Georg von Trapp went to Cattaro to take command of U-5. The Austro-Hungarian navy had only seven submarines, all of which suffered from mechanical weaknesses. Unrestricted submarine warfare had yet to commence, so U-boat commanders were not free to hunt what they chose. The Austrians had orders to stay away from neutral-flagged merchant ships. They attacked cargo vessels according to “cruiser rules,” meaning stopping the ship and warning the crew before sinking it or taking it as a prize. Moreover, the Austrians had few other targets because Allied warships generally stayed out of the Adriatic after the Austrian U-12 torpedoed and damaged the French dreadnought Jean Bart on December 21, 1914.

Trapp decided that he would have to look elsewhere for prey. Word had reached him of an enemy cruiser, one the Austro-Hungarian navy had been unable to catch, making periodic appearances in the Otranto Strait. The short-ranged U-5 could just make it there.

Trapp would later write of his experiences in To the Last Salute: Memories of an Austrian U-Boat Commander, published in German in 1935 but not available in English until 2007 (and from which most of the quotes in this article are taken). He was happy to be back in a submarine, having spent the early days of the war in a torpedo boat, duty he found uninteresting. Nevertheless, U-5 had its idiosyncrasies—some of which nearly killed him.

The worst was what his crew called “gasoline stupor.” The engines ran on gasoline, not diesel. The U-boat lacked compartments, and its worn-out engines filled the submarine with gas and exhaust fumes. If the sub submerged without ventilating, crewmen could become unconscious in thirty minutes. Additionally, the periscope mechanism was a clumsy affair. Although it could be raised and lowered, the process was so slow that it was more efficient to alter the submarine’s depth. At 250 tons, the boat was also quite small.

U-5 slipped its moorings two days after Trapp took command. That night, after a fruitless day of searching, a crewman spotted smoke. Trapp ordered a change of course, toward the sighting. They ran on the surface at full speed to intercept the vessel. The mast of an enemy warship soon appeared over the horizon; it was coming in fast—too fast, Trapp decided. He ordered a dive.

Trapp brought U-5 up from time to time to get a better look. He spotted the ship, consulted his recognition book, and identified it as a French cruiser of the Victor Hugo class. He brought the submarine up for another glance, then another, but this time he saw nothing.

“I feel foolish,” he wrote later. “During the night the enemy ran right into my arms, but I let him escape.” Trapp decided that the cruiser would be careless in the darkness, and if he was patient he might get another chance.

The submarine’s crew found the cruiser again the next night, silhouetted against the moon. Trapp began his approach, planning a surface attack. However, the enemy surprised him by turning, then hurrying away.

Trapp decided to try yet again the next night, but it would be his last chance; U-5’s fuel was dwindling. During the day, he studied his charts and analyzed the cruiser’s behavior. On the previous two nights the enemy ship had approached from the southeast. When it reached a point ten nautical miles from land, it began a slow back-and-forth pace so it made less smoke. Then, after midnight, the cruiser would head for the open sea, moving southerly, toward home.

That evening, the night of April 26-27, U-5 cruised about fifteen miles south of Cape Santa Maria di Leuca. The enemy ship came on as expected. Trapp spotted it around midnight, backlit by the moon, slowly sailing northward as he had anticipated. U-5 approached on the surface to within eyesight, then submerged. Trapp had elected to make his nighttime attack at periscope depth, gambling that enough light would penetrate the lens for him to take the shot. It would be the first time an Austrian submariner had attempted such a feat. But when he looked through the periscope, at first he couldn’t find the cruiser. Then he spotted “a minute speck.”

Trapp kept an eye on his target. It turned, heading toward him. The ship began to fill the crosshairs of the periscope: the bow, the forward superstructure, the bridge, the stacks, and with them, the ship’s heart—its boilers.

Trapp ordered the starboard torpedo fired, then sent the port fish after it. The enemy ship had no chance to evade. The torpedoes made forty knots, and U-5 was only five hundred meters away. “There—a dull, hard sound,” Trapp wrote, “after ten seconds a second one, as if a knuckle hit an iron plate, and a cloud of smoke shoots high up, far above the topmasts.” The crew cheered.

The cruiser began to list, and its crew struggled to launch lifeboats from the port side. It was Léon Gambetta, a 12,500-ton armored cruiser, flagship of the French 2nd Cruiser Squadron commanded by Rear Admiral Victor Baptistin Sènés. As chaos engulfed the sinking vessel, the admiral restored calm, Anthony Sokol wrote, by telling his crew, “Don’t be in such a hurry; the boats are for you; as for us, we shall stay here.” By “us,” he meant the officers. They were among the 684 men lost when the ship went down only nine minutes after U-5 launched its torpedoes.

When U-5 surfaced, Trapp was amazed to find that the cruiser had sailed without escorts. He spotted five lifeboats in the water, which presented an unexpected problem: What to do with the survivors? Trapp discussed it with his two fellow officers. They could take no one aboard, and the survivors could not cling to U-5. They would be safer in their lifeboats, so that was where the Austrians left them.

The great loss of life caused by the sinking, combined with having to leave behind the survivors, greatly upset Trapp. “So that’s what war looks like!” he wrote. He reluctantly ordered the engines started, and they headed home to Cattaro.

The Austrians feted Trapp and his crew as heroes upon their return. Léon Gambetta was the first ship the Austrians had sunk during the war. A grateful nation decorated U-5’s crewmen, and Trapp received the prestigious Order of Maria Theresa.

Trapp’s success caused the French to change their Adriatic theater operations. Admiral Augustin Boue de Lapeyrére, commander in chief of French Mediterranean forces, forbade virtually all ships of cruiser size and larger from venturing into the Adriatic beyond the Greek island of Cephalonia, at the Gulf of Corinth. The French fleet itself withdrew even farther, to Pylos, in the south of Greece, which became a base for the Allied fleet blockading the Otranto Strait.

On April 26, the Italians signed the Treaty of London, committing Italy to the Allied cause within a month. Italian naval might added to the weight of forces arrayed against the Austrians but did not significantly alter the strategic balance in the Adriatic. Admiral Anton Haus, commander in chief of the Imperial and Royal Austro-Hungarian Navy, responded to the Italian declaration of war by sending out the Austrian fleet on May 23 to launch surprise bombardments along the Italian coast. For a time, he kept Trapp’s U-5 and the other Austrian submarines in reserve.

Vice Admiral Luigi Amadeo di Savoia commanded the Italian fleet. He wanted to capture the Austrian islands of Lagosta and Pelagosa as part of a line of posts he hoped to establish across the Adriatic to the Dalmatian coast. Italian troops landed on unoccupied Pelagosa on July 11.

U-5 was moored at Lissa when Trapp received word of an Italian submarine at Pelagosa that had been brought in to help defend the island. Trapp set off at nightfall, hoping to catch his prey before sunrise. U-5’s crewmen had to fight foul weather on the way, but the storm began abating not long after they spotted Pelagosa. Because of the storm, Trapp believed the Italian submarine would be positioned to the south of the island, on its lee side, in a large bay. He planned to bring U-5 to about three miles out around 0330 hours, submerge, and then enter the bay and reconnoiter.

Trapp gave his orders and went below, an unpleasant experience. “Everything is damp,” he wrote. “Water drips incessantly from the ceiling overhead, which is finished off with small cork pieces.” U-5 had no berths, so everyone slept on the lower deck, the enlisted men on woolen blankets, their faces masked to protect them from the falling water. The officers slept on two leaky air mattresses thrown down beside the torpedo tubes.

They submerged at daybreak on August 5. Trapp surveyed Pelagosa through the periscope, studying the gray-black rocks, the great lighthouse, and the white stone beach. He brought U-5 into the bay, and soon they were only three hundred meters from shore. Trapp strained to see through the periscope, eyeing the coast. “Sweat drips from my forehead and my shirt sticks like a wet rag to my back,” Trapp wrote. “From time to time I wipe the eyepiece, which constantly mists over and impedes the view.” He ordered the boat raised one meter.

Trapp spied the flag first, the green-white-red banner of Italy, their hues breaking out from the inky rocks. Then he saw the Italian submarine, lying near the shore, its gray hull barely discernible, and its crew on the sand. At that point, the Italians spotted U-5’s periscope. The meeting became a race.

Trapp had not found his enemy quickly enough. U-5 had already gone past the point where he could fire, and the enemy sub was too close for him to simply turn and take a shot. U-5 had no rear torpedo tubes, so he had to bring the boat completely around before the Italians got underway and launched their own strike.

The Austrian commander watched his compass. When the boat had turned 320 degrees he ordered it brought back up to periscope depth, then looked around. The Italian sub, Nereide, was already underway and half-submerged. Moreover, the enemy vessel was capable of launching a torpedo at a 35-degree angle. Worse, Trapp realized that he’d brought U-5 too far around and had to turn back before he could attack. In turning back, he came directly in the enemy’s line of fire.

Nereide fired and Trapp watched the line of bubbles streaking out from the Italian submarine, straight toward U-5. The Austrians heard the whirring of the torpedo, braced for its impact—and listened to it pass by harmlessly.

Trapp studied his target and aimed. He ordered the starboard torpedo fired, then the port. The crew’s nerves were at the breaking point, and Trapp nervously chewed on his moustache as he tracked U-5’s torpedoes. The first missed, passing forward of the Italian sub. The other hit solidly. A tower of water spiked into the sky, a dirty cloud following it, and the resulting shockwave shook U-5. The water fell, then the smoke cleared—and there was nothing left. Nereide was simply gone. A lone sailor dressed in white and blue, more fortunate than his comrades in being too slow to get to his boat, paced the shore.

Trapp pointed U-5 toward open water. Gunfire from the shore began striking the sea around the Austrian sub. Trapp took it down to twenty meters, but they were scarcely away when both engines broke down. U-5’s crew made temporary repairs and nursed the boat into the Bocche di Cattaro the next morning.

While at Cattaro the Austrians received word that an Italian Quarto-class light cruiser was twenty nautical miles off the Adriatic coast, near Lagosta. On September 13, 1915, U-5 left port in case the Italians decided to seize any more of the islands dotting the Dalmatian littoral. By that evening, Trapp had taken up a position where the enemy ship had last been reported. A storm blew up, making it impossible to see, much less attack. Trapp put his boat on the bottom, killing the engines to pass the night and let his men sleep.

A calm sea greeted U-5’s crew when they surfaced at dawn, with a heavy fog bank sitting about six miles away. The Austrians had come up on deck to smoke, swim, and breathe some clean air when the Italian cruiser emerged from the fog bank, heading in their direction. Someone sounded the alarm, and the submariners scrambled below.

Trapp ordered both torpedo tubes prepared as he studied the enemy ship through the periscope. Just then one of the crewmen was brought up and laid at his feet unconscious, suffering from gasoline stupor. The sub had not been properly ventilated before they dived. Within minutes five men were out cold on the deck. Nausea, headaches, and drowsiness gripped other crewmen.

Soon only Trapp, the two other officers, and three men remained alert. Trapp struggled to stay conscious, guiding his boat toward the target—not too fast, because the scope would then leave a wake, but fast enough so that he could make the attack before the fumes overtook them. When he could no longer stand, he called for a folding stool. He ordered Gottfried Hermann, his machinist’s mate, to revive him in three minutes, and passed out. Hermann stood beside him, stopwatch in hand, ticking off the time. When he shook his captain awake, Trapp peeked at the enemy, told Hermann to wake him again in one minute—and passed out a second time. Hermann marked the seconds, then shook him awake. Then again in thirty seconds. Then in ten.

They struggled to maneuver the sub into a firing position. Its bow grew heavy, dragging them down, making the boat difficult to control. Trapp ordered full power and the bow came up, the rudders slowly steering the boat to periscope depth. Finally the periscope breached the waves. Three or four minutes had passed since Trapp had last seen the cruiser—too long, in his estimation. He twisted the scope in every direction but saw only sea and sky. Worse, the sub had surfaced too fast. It burst out of the water and slammed bow-first into the waves.

Now Trapp spotted the cruiser, which had passed them and changed course. It made straight for U-5’s wash at top speed, safe from attack, since the sub had no aft torpedo tubes. Trapp watched the gunners race across the enemy ship’s deck as he once again submerged. When he came up for another look, the cruiser was safely away. After fifteen minutes, U-5 surfaced once more. This time the crew ventilated the sub as they brought the crewmen who were still unconscious out on deck.

Trapp was bitterly disappointed. He had missed a rare chance and was sure he could have sunk the cruiser had it not been for the poor quality of his sub. He lamented, “And with such junk we must wage a war!”

In October Trapp received a new command, U-14, formerly the French submarine Curie. On December 20, 1914, when the sub’s French commander had tried to penetrate Austria’s Pola Harbor, its prop became tangled in the protective net. Unable to escape, Curie was forced to surface when its air became foul. The waiting Austrians sank the sub, then raised and repaired it.

The Austrians found the vessel had been haphazardly constructed. For example, none of its valves, cocks, or switch handles worked the same way. Trapp’s new boat did have compartments, berths for the men, a mess for the officers, and centralized diving controls. At 407 tons, it was the largest submarine in Austrian service throughout the war. But the new boat’s foibles extended beyond its arbitrary controls. Sometimes it could take as long as fifteen minutes to dive. Its unreliable engines also plagued the crew, as had U-5’s power plants.

In addition to internal tubes, U-14 had exterior-mounted torpedoes that proved particularly troublesome, and in some respects dangerous. The torpedoes were mounted on swivels in insets along the sub’s side, near the top of the hull. They could swing out to about a forty-five-degree angle, allowing shots not in line with the bow. The exterior torpedoes proved difficult to aim and were subject to damage, especially from depth charges. This weapon system failed Trapp on more than one occasion.

The Bulgarians entered the war on the side of the Central Powers in September 1915. In October a German, Austrian, and Bulgarian offensive overran Serbia and the Serbian army retreated to Albania. Soon the Allies began evacuating the Serbians. The Austrian navy did little to hinder these operations, missing a great opportunity, but Admiral Haus believed the southern Adriatic was simply too dangerous for his large warships. The Austrians did take some actions, one of which was to dispatch submarines to hinder the Allied evacuation.

The captains of U-14 and U-4 planned to launch a combined assault on the Allied merchant ships entering Albania’s Durazzo Harbor, one boat striking from the north, the other from the south. They found their targets entering Durazzo the next morning as expected, and Trapp set up U-14 for what he thought would be an easy attack. At five hundred meters from the target, he gave the order to fire. The shot went wide, the torpedo following its own path. The crew had a bow torpedo ready, but the next target was beyond its firing radius.

Trapp looked around. A French torpedo boat passed just fifty meters away, its machine gun firing at the sub’s periscope. Trapp laughed as he watched the sailors’ futile effort. Then he remembered that these ships carried a new weapon—depth charges—and his mood sobered.

U-14 submerged to twenty meters, turned, and made a run for it—but not quickly enough. An explosion rocked the water, and blackness engulfed the sub’s crew. A second blast shook the boat. One terrified crewman yelled for them to surface. Trapp ordered silence, and the crew rigged up some portable lights that allowed them to see well enough to steer. An officer started their gramophone as a distraction, after which the strains of “O Blue Adriatic” were punctuated by the nearby depth-charge blasts.

The helm wouldn’t respond, and U-14 settled on the bottom at fifteen meters. Trapp ordered the engines stopped; if left running, the sub’s screws would have muddied the sea, giving away their position. The crew could hear the sound of enemy propellers draw near and then fade, the thumping of the depth charges trailing away into the distance.

Now the sub’s crew had a new problem: The mud held U-14 captive. The only way to escape was to blow both tanks, but the Austrians didn’t want to surface, so as soon as the boat left the bottom Trapp planned to reflood the tanks while giving both engines maximum power, then use the diving rudder to keep U-14 under water.

Things didn’t go as planned, however. The boat, stuck fast in the mud’s grip, required more power than expected to rip free. When it did escape, it didn’t accelerate quickly enough. The whole superstructure broke above the waves, and Trapp saw three destroyers charging toward them, guns firing. He took the boat down to fourteen meters, hoping the enemy had no aircraft around for spotting. Depth charges exploded far astern; one of Trapp’s crewmen guessed that they were hitting the sub’s former mud bed.

U-14 headed for the open sea, but the attacks had smashed the bilge pump shaft, and the sub was taking on water from leaks. When Trapp came up to look around, he saw the trio of Allied destroyers following fifteen hundred meters astern. He turned U-14 ninety degrees, then checked again, but the enemy was still there. Trapp veered another ninety degrees and descended to twenty meters. By now concluding that the enemy had sound detectors, he quieted the sub and changed course, doubling back and forth and dropping to twenty-five meters. All was silent except for the sound of the electric motors.

U-14 had been submerged for twelve hours, and its air was foul. Some crewmen labored in their underwear, sweat dripping. Anyone who was not working lay down to conserve precious air. Soon their heads felt like iron weights, and the tiniest task became nearly impossible. Still the destroyers hung on.

Trapp finally figured out how the enemy was tracking him: U-14’s oil tanks had been damaged by the depth charges, and the sub was trailing oil. But the deeper it went, the longer the trail would become and the farther the enemy ships would drop behind. Here was the key to escaping.

First, though, Trapp had to get fresh air into the boat. U-14 went down to thirty-five meters, the submarine groaning from the pressure. The Austrians had only tested the sub to twenty-five meters, but Trapp was sure it would survive the maneuver. He then ordered the boat to come up quickly to ten meters, and looked around. The destroyers were about twenty-five hundred meters away. U-14 surfaced, and Trapp popped open the hatch. A crewman named Mayerhofer had orders to put the engine in gear when his captain did this, drawing air into the submarine. Meanwhile Müller, his youngest officer, handed Trapp a bucket of oil for him to fling into the sea. The destroyers were coming in their direction and firing as U-14 dived.

When Trapp surfaced next, the destroyers were gone. The trick had worked, and the Austrians headed for home. Two of U-14’s fuel tanks were leaking, and all the external torpedoes had been shattered, but—like U-5U-14 made it back to port. A few days later, the Allies reported having sunk an Austrian submarine off Durazzo. “We grant them this satisfaction,” Trapp wrote.

Trapp took U-14 out again after the failed sortie against Durazzo, but horrendous mechanical problems made it a short cruise. The boat was in such poor shape that it was more dangerous to its crew than to the enemy. When U-14 entered Pola the rudder broke, sending the sub into a minefield at full throttle. The mines were moored at a depth of two meters, and Trapp chalked up their survival to nothing less than the presence of “all the guardian angels.”

After that Trapp won approval to have the sub completely rebuilt, a process that dragged on for months. However, U-14 was far safer and much more effective when it reentered service, just in time to take part in the war’s major submarine campaign.

In April 1917, The Germans had declared unrestricted submarine warfare in hopes of driving Great Britain out of the war, and the Austrians followed suit. Virtually all merchant ships became targets. Now, however, the Austrian and German subs had to run the Allied blockade of the Otranto Strait. Trapp took a couple of hours to pick his way through the armed trawlers, spotting the masts of ships and then maneuvering U-14 headed for the Mediterranean. away. Once in the open, U-14 hunted in the sea lanes running from Cape Matapan to Crete, the passage for freighters bringing supplies to the French troops in Salonika, Greece. Trapp began by searching to the west of the Greek islands of Cerigotto and Cerigo, which lay along this route.

U-14’s crew eventually spotted a lone steamer heading toward Cape Matapan, probably coming from the Strait of Messina. The attack, made at night, proved an easy one, with U-14 torpedoing the steamer amidships. It didn’t sink immediately, and Trapp watched the lifeboats launching, noting that there was a crewed 120mm gun on its deck. He brought U-14 in under the gun’s depression, surfaced, and opened fire. He later described the moment when the ship finally went down during the night: “The moon is behind the steamer. It is a magnificent scene—the ship, as if it were a mortally wounded wild animal, rears up for the last time, lifts the bow steeply out of the water, stands still a moment, and then sinks perpendicularly into the deep.”

The sub found its first convoy several days afterward, sailing in two columns, screened by trawlers. For the Allies, convoying was a relatively new tactic, started late in the spring of 1917. They had previously protected their merchant ships by patrolling the trade routes, which accomplished virtually nothing. Trapp likened the new development to the Spanish of Philip II shepherding their silver ships to protect them from pirates, calling U-boats “the most dreadful pirates of all time.”

Trapp watched the convoy for an hour, seeking to uncover the pattern of the enemy’s zigzag course changes. He soon figured out that the convoy shifted course twenty degrees every quarter hour, first turning starboard and then to port. Trapp took the sub down, intending to sneak in between the two columns from the front, moving toward the place where he believed he was least likely to be found. He sized up the biggest merchantman, planning to launch a broadside of torpedoes.

U-14 entered the convoy head on. Trapp watched the first ship go by, then saw the next vessel send up an alarm: blotches of white smoke from the steam pipe on its stack. A scant three hundred meters away, it turned in an attempt to ram the sub. Trapp looked from the steamer to his target, hoping to torpedo it before the other ship could hit his own vessel. He decided he had time, quickly swiveled the periscope once again between the two ships, and gave orders to fire, drop to twenty meters, and lower the periscope. U-14’s crew waited for the sound of the explosion, but nothing came. Trapp cursed as the whirring sound of the steamer’s propellers passed above. He raised the sub back up to periscope depth and looked around.

He had missed his chance at the largest vessel, but there was still good hunting. Trapp targeted the next ship and brought U-14 around in a circle, firing a torpedo that hit the freighter’s stern and blew up its boiler. The trawlers drew nearer to help the stricken merchantman, ignoring the U-boat as it withdrew.

Despite this success, Trapp was incensed about the first torpedo and asked his crew to find out whether it had even been launched. The torpedo officer looked over everything, and although nothing appeared to be wrong, the torpedo had failed to fire. This made Trapp even angrier at losing such a fat target. Then he remembered the remorse he had felt only a year earlier after sinking Léon Gambetta. “Yes, yes,” he wrote in his memoirs, “I have lost compassion for the drowning enemy; he has none either.”

Trapp soon shook off these notions and went back to work, bringing U-14 to the surface and following the convoy. He still wanted to bag the big ship. The screen of armed fishing trawlers began firing at the sub, but U-14’s new 88mm deck gun outranged their weapons, forcing the trawlers to retreat. That afternoon brought foul weather, and the convoy disappeared behind haze and mist.

Since the hunt had already carried them so far westward, Trapp decided to make for the Strait of Messina. U-14 arrived after dark, finding the coast ablaze in lights. The U-boat submerged to pass Messina, then moved on to hunt elsewhere, soon spotting a small merchant ship with a torpedo boat and a gun-bearing yacht for protection.

Trapp’s plan of attack required a tricky move: diving under the yacht and then climbing to attack depth. Although his crew successfully managed the maneuver, once again the torpedo didn’t launch. This time it was the fault of a new Czech crewman who didn’t comprehend that all commands and instructions had to be repeated back to ensure the orders were understood.

Returning to the vicinity of Cape Matapan, U-14 sank a Greek freighter, Marionga Gulandris, on a moonlit night. “He came straight for me,” wrote Trapp, “practically ran into my arms.” From the Greek captain he learned that the steamer had carried 4,500 tons of wheat from Baltimore, Maryland. “On the entire long trip nothing had happened to him, and now, a couple of hours from his destination, bad luck caught up with him,” Trapp remarked. “It’s tough, but after all, that is war.”

After a thirty-day cruise, U-14’s torpedoes were gone and its fuel was nearly exhausted, so Trapp set a course for home. Following a surprisingly easy passage of the Otranto Strait, he wondered if events elsewhere might have smoothed the last leg of the trip. Once he reached shore, however, his fellow submariners laughed when he  asked if the war had ended; the strait was clear because the Austro-Hungarian navy had mounted a raid against the blockade.

The Allies gradually strengthened their blockade of the Adriatic, adding more and more vessels to what became known as the Otranto Barrage. Allied planners hoped to contain the U-boats within the Adriatic or force them under and exhaust their batteries and air. Trawlers patrolling the passage pulled nets rigged with explosives. Planes searched for submerged U-boats.

Sailing on August 20, 1917, Trapp attempted to make it through the barrage at night. It proved a rough trip. He dodged a body of destroyers, then bluffed his way through part of the passage by flashing a random answer to a signal, a ruse suggested by one of the junior officers, a Hungarian named Sándor Ilosvay de Nagyilosva.

The next morning a group of a dozen trawlers forced them to submerge. To escape the nets towed between each pair of boats, Trapp sailed on a parallel course with the enemy ships, allowing them to overtake and pass U-14, all while maneuvering between the trawlers, avoiding their nets, and keeping his periscope or its wake from being spotted. U-14 remained undetected, but spent the rest of the day ducking other enemy squadrons. Only when night came could they finally surface.

Trapp was exhausted. He had spent the previous twenty-four hours in the conning tower or at the periscope. Too tired to eat, he decided to get some sleep. The alarm rousted him from his berth a little after midnight, when U-14 crash-dived to avoid a destroyer. Fifteen minutes later the sub was back on the surface and finally through the strait.

It took two more days for U-14 to reach its patrol area. At this stage in the war, merchantmen generally plied two sea lanes: Cape Passero to Cerigo, with cargo destined for Salonika and the French troops in Macedonia, and Malta to Port Said, Egypt, to supply the British forces in Mesopotamia and the Suez Canal region. Trapp initially chose the Cape Passero route.

U-14’s first victim was a French vessel in convoy. After neighboring ships had rescued the survivors and then moved on, the sub surfaced. Debris from the sunken ship supplied useful items such as bags of flour and casks of fresh water.

Certain the Allies had deduced U-14’s location, Trapp began working the route between Malta and Port Said. The next morning the sub caught a convoy of five steamers moving in two lines. Their four escorts altered course and speed unpredictably, sometimes even dropping depth charges after suddenly dashing off to some point. Trapp pronounced this stratagem crafty—and amusing—as he moved to attack, heading between the two columns into the convoy. He was forced to let the destroyers cross over U-14 twice before attacking. The first target was three hundred meters away. He waited for the right moment, and fired. Trapp watched the torpedo through the scope, running true. Then nothing.

“There is just enough time for a curse,” Trapp wrote, deciding the torpedo had run too deep. A destroyer came at U-14 just then, slinging depth charges, and a second steamer turned, hoping to ram the submarine. Instead of diving deep immediately, Trapp stuck it out and ordered a second torpedo fired before taking his boat down to twenty-five meters and ducking under the other line of steamers. The destroyer’s depth charges chewed the water astern of the sub as the merchantman went down.

The next day U-14 caught a convoy coming from the west, but when the steamers made an unexpected turn, Trapp lost his chance to attack. The Austrians gave chase, however, catching up with the Allied ships during the night and sinking one of them. Afterward they looked for the name of the ship among the drifting lifeboats, but it had apparently been removed. What they did find was a pair of blue trousers in a lifeboat. One of the crew took them as a prize.

Continuing the chase, the following day U-14 torpedoed another steamer, the thirty-seven-hundred-ton Nairn. The loot was much better this time: “Lard, margarine, oil, flour, sugar,” Trapp recalled— all hard to find in wartime Austria. The crew fished out a crate marked “Fragile,” hoping it might contain whiskey, but found it held lamp chimneys. The men threw it back into the sea amid much cursing. They also found a jacket that matched the pants rescued a couple of days before. Trapp told the happy recipient that he would next try to “shoot” him a vest.

U-14 intercepted a wireless communication about its last two victims and, knowing that the Allies generally shifted their convoy routes twenty miles north or south after U-boat attacks, sailed northward. The guess proved a good one. That night they found a convoy of three steamers with two Foxglove-class submarine chasers coming from the west. U-14’s crew put their boat in front of the convoy and waited for morning, diving at 0500.

Trapp steered a course between one of the escorts and a steamer on the right side to line up a shot at the biggest freighter. He brought U-14 in behind the escort to avoid colliding with the merchantman trailing behind it. Trapp looked through the periscope as they moved, saw the wall of a ship, and ordered full stop: He had nearly slammed into one of the escorts, which cut over U-14’s nose, its stern-mounted depth charges almost brushing the sub’s superstructure.

Trapp turned to line up an attack on the biggest merchantman, but the enemy had spotted him. Instead of heading toward U-14, however, the alerted subchaser ran to the fringe of the convoy, where the skipper seemingly believed the threat lay. Trapp waited while another freighter briefly blocked his firing path. By the time he had a clear shot, the big ship was so far in front that he could only send his fish after its stern, rather than at its profile, as it drew away. Despite the difficult shot, his torpedo slammed into the giant steamer.

Trapp ordered a dive to thirty meters, hoping to avoid the expected counterattack. The subchasers laid their eggs in the wrong place, however, and U-14 was soon up and looking around again. The damaged freighter dropped its lifeboats, and one of the escorts came alongside, apparently to offload crewmen. Trapp watched the shepherding warship move around a bit, stop, then steam away. Unsure what was going on, he took U-14 ten thousand meters away from the injured freighter and surfaced. He was curious but also wary.

The ship’s delicacies were a great temptation to Trapp and his crew, but the captain remembered a saying among the U-boat men: “What one cannot identify one must regard as suspicious.” He remained on guard as they slowly drew nearer to the ship and fired some shells into it as a test, then a few more. They shortened the range, observing the damage done by their fire but seeing no crewmen aboard the steamer.

The Austrians decided to board and investigate, but Trapp remained ill at ease. He was also unsure how to get his men aboard until he hit upon the idea of using one of the ship’s lifeboats, bobbing nearby. He shifted the sub to take up the closest boat. It proved a lucky move: As soon as U-14 changed course, a hidden gun on the freighter opened up, and one of the escorts reappeared in the distance.

Fortunately for U-14, the enemy gunner was a poor shot. Trapp ordered a crash dive, and the crewmen were rushed forward, with both engines pushed to full power. The Austrians attempted to finish off the freighter with a second torpedo, firing it at four hundred meters. However, the torpedo started to slow, rose to the top of the waves, turned 180 degrees—and sank. Trapp didn’t have time to figure out what was going on; the escort had arrived. U-14 expended a third torpedo on the great ship, and the detonation tore it in half. When the water and smoke cleared, the vessel was gone.

Trapp ordered U-14 to reverse, and a screeching noise rippled down the entire length of the hull. Later they realized the escort had laid a net around the damaged ship, hoping to ensnare the enemy sub. This was the source of both the disconcerting sound and the second torpedo’s curious movements.

The Allied escorts rushed in to save the survivors as U-14 slipped away. With all his torpedoes expended, Trapp pointed the sub toward home. It was September 1, and U-14 had been at sea only nine days, but during that time, it had sunk 24,800 tons of shipping. Its last victim, the Italian freighter Milazzo (11,480 tons), proved to be the biggest merchant vessel sunk by the Austrian navy during World War I.

U-14 was not yet in the clear, however, as the escort continued to shadow them. Trapp peeked through his scope at ten-minute intervals for the next two hours, and each time saw the enemy ship still trailing them, crossing back and forth over the sub’s path. Its presence meant U-14 had to remain submerged.

The U-boat’s batteries grew weaker, but the enemy kept trailing. Trapp became frustrated, complaining that dealing with the one freighter had occupied them for fifteen hours. Now he had no choice but to surface, because he desperately needed fresh air in the boat. He decided he would have to “count on poor English eyesight” for protection.

In preparation, Trapp told the engineer to keep the engines from belching black smut when started. But the moment the first engine turned over, it sprayed an inky black plume into the sky that Trapp likened to a burning oil tank. The second engine added to the revealing black cloud. Nevertheless, Trapp won his gamble. Either the British crew didn’t see the dirty clouds, or mistook them for steamer smoke.

U-14’s return passage through the Otranto Strait proved much easier than its exit. The sub submerged to avoid a flotilla of destroyers, then dodged the trawlers while running on the surface. The following morning found them safely in the Bocche di Cattaro.

Trapp made many other cruises during the war. On one memorable occasion he was forced to rush to the bridge another au natural. On another, he was left momentarily clinging to the top of the raised periscope when his sub began submerging under him. But on none of these voyages did he do as much damage to the Allies as on the cruise of August-September 1917. During the course  of the war, Trapp sank a total of 44,595 tons of merchant shipping, making him the most successful submarine commander in the Austro-Hungarian Empire.

In March 1918, the Austrians sent Trapp to Romania to inspect a captured Russian submarine, a boat he pronounced too tiny and dilapidated for service in the Adriatic. On his return, he was named head of the submarine base in the Bocche di Cattaro, his last command of the war.

Defeat in November 1918 deprived Austria of its seacoast and Trapp of his beloved navy. When he left his homeland for the final time, one of the things he stuffed into his backpack was the imperial ensign he had personally lowered at the end of the war in a ceremony that, to Trapp at least, marked the death of both the Hapsburg Empire and its navy.

In 1922 Trapp’s wife Agathe died of scarlet fever. In many respects, those twin blows left him a broken man. But four years later a young woman named Maria came to his home to look after one of his ailing daughters. She would eventually marry the famous captain. And together they would sing.


Originally published in the Spring 2008 issue of Military History Quarterly. To subscribe, click here