When a large explosion rocked the Quai de la Seine in northeast Paris at 7:18 on the morning of March 23, 1918, no one at first knew what had caused it. No German air- craft were visible, and although Germany had initiated its great Spring Offensive of 1918 just two days earlier, enemy ground forces remained well over 60 miles north of the French capital. No known artillery piece could fire a projectile even half that distance. The preliminary conclusion was that some sort of new high-altitude airship had dropped a large bomb. But then, about 15 minutes after the first explosion, there followed a second one, then another 15 minutes after that. By day’s end Parisians had counted 21 similar explosions.
Within hours ordnance experts had recovered enough ballistic evidence from the various impact sites to determine that Paris was in fact being shelled by a gun or guns firing approximately 8-inch rounds. But that seemed impossible. One working hypothesis surmised the Germans had somehow infiltrated a gun far behind French lines, perhaps into the forests just outside Paris. By the next day, however, the French had gathered enough additional evidence to prove conclusively the shells had come from behind German lines, specifically from somewhere in the Forest of Saint-Gobain near Crépy, just northwest of Laon. But that was nearly 80 miles away. The only logical conclusion was the Germans had secretly developed and fielded a supergun.
In fact, they had fielded three.
The Germans had two names for the long-range artillery pieces bombarding Paris: (“Wilhelm Guns”), in honor of Kaiser Wilhelm II, and Pariskanonen World War I the British and American press, and even (“Paris Guns”). But for many years after Wilhelmgeschützen many historians, mistakenly called them “Big Berthas.” The Dicke Bertha, however, was a completely different gun—a siege howitzer that fired 420mm concrete-piercing shells the Germans used to demolish Belgian fortresses in 1914.
The Paris Guns are among the most remarkable artillery pieces in military history. Their estimated maximum range of 82 miles far exceeded that of any operational gun built up to that time or since. Even today the Russian 203mm 2S7 Pion can achieve its maximum range of 34.5 miles only when employing a rocket-assisted projectile. In 1918 the Germans used conventional ammunition. The ordnance engineer who designed the Paris Guns was the brilliant Fritz Rausenberger, a director of the German arms-manufacturing giant Krupp AG. He had also designed the Big Bertha.
Krupp had a long tradition of ordnance research and development. Rausenberger for some time had worked through the problems of achieving ranges in excess of 60 miles. In 1916 he approached Oberste Heeresleitung (OHL), the German army High Command, seeking official support for a gun specifically designed to bombard Paris. Colonel Max Bauer, one of the more influential General Staff officers at OHL, convinced both Field Marshal Paul von Hindenburg—chief of the General Staff—and his able deputy General Erich Ludendorff to support the project. By late 1917 Krupp had a working prototype, and it successfully fired the first gun on November 20 at the Altenwalde test range near Cuxhaven on the North Sea coast. After additional experimentation with propellant and projectile combinations, the Krupp engineers achieved a range of just over 78 miles on Jan. 30, 1918. Krupp immediately started manufacturing additional carriages and at least seven barrels.
Krupp assembled the barrel of each Paris Gun by inserting a 210mm liner tube into a bored-out 56-foot 380mm SK L/45 “Long Max” naval gun barrel. The liner extended 36 feet beyond the muzzle of the main barrel. A 20- to 30-foot smooth-bore extension was then attached to the front of the protruding liner, resulting in a composite barrel with an overall length exceeding 110 feet. An external truss system clamped atop the barrel reduced the droop of the tube caused by gravity. Krupp engineers had to mount a massive counterweight on the breech in order to elevate the gun for firing and depress it for loading. The carriage was a steel box assembly, with a pivot in the front and wheels in the rear that ran on a circular track. The gun could only be moved to its firing position by rail, assembled in place and fired from a prepared concrete firing platform. The barrel alone weighed some 140 tons, the carriage 250 tons, and the turntable-type firing platform 300 tons.
As might be expected, a Paris Gun was not easy to operate. Weighing either side of 400 pounds, the propellant charge could produce a chamber pressure of 69,600 pounds per square inch and a bore temperature in excess of 3,600 degrees Fahrenheit. The corrosive propellant composition eroded several centimeters of steel from the barrel with each shot fired, thus increasing the volume of the firing chamber. After loading the next round, the gun crew had to measure the firing chamber volume and then increase the subsequent propellant charge accordingly.
In early test firings the extreme temperatures and pressures tore the traditional copper rotating bands right off the projectile body, preventing the round from spinning properly in flight. The solution was to machine rifling grooves with a 1-in-35 twist into the steel body of the projectile. Thus, the crew literally “screwed” each round into the chamber on loading. That solution worked, but it also drastically increased the wear on the bore, expanding its internal diameter with each shot. That, in turn, meant each succeeding round had to be slightly larger than the last. Each barrel, therefore, came with its own dedicated set of projectiles, numbered sequentially in exact firing order. Such attention to detail did not eliminate error, however; a mistake in the firing sequence on March 25 caused a tube detonation on the No. 3 gun, killing or wounding 17 men. Each tube had an estimated service life of 60 rounds, with round No. 60 having a diameter of 222mm. After that the crew replaced the barrel and sent back the old tube to the Krupp factory in Essen, where it was re-bored to 224mm and then reissued with a new set of shells. After the second set of 60 rounds the tubes were re-bored a second time, to 238mm.
The Paris Guns achieved their startling maximum range by seeming to defy the normal laws of ballistics. All artillery pieces, before and since, fire at their maximum range when the barrel is elevated to an angle of 45 degrees, or 800 mils. Anything over 45 degrees is classified as high-angle fire. As the elevation increases beyond that point, the shell goes higher, but the range decreases. The Paris Guns, however, achieved their maximum range at an elevation of 50 degrees, or 889 mils. Two factors contributed to this phenomenon. The first was the Coriolis effect with regard to the rotation of the earth. The round’s time of flight from the firing point in Crépy to Paris was 177 seconds, almost three minutes. With the gun firing southwest and the earth rotating from west to east, that three minutes of flight added more than 600 meters to the achieved range—and also pushed the shell somewhat to the right.
The more important range factor, however, was what gunners call the maximum ordinate—the height the shell reaches in its trajectory. At 50 degrees elevation the shells from the Paris Guns reached an altitude of 138,800 feet. Reduced air density at higher altitudes causes far less drag on the body of the projectile, which resulted in the greatly increased horizontal range. The shells fired from the Paris Guns were the first man-made objects to reach the stratosphere, an altitude record they held for nearly a quarter century, until the Germans test-fired the first V-2 missiles in late 1942.
Despite the Paris Guns’ incredible range, the tactical effect at the target end was less than impressive. The average projectile weighed 234 pounds, but much of that mass was in the body of the shell, which required reinforcement to withstand the massive firing pressures. The explosive charge itself was a mere 33 pounds, only a quarter of the total shell weight. The combination of the low explosive change and the thick shell body produced a small explosion with relatively few, though large, fragments. One shell that landed in Paris’ famed Jardin des Tuileries left a crater just 10 to 12 feet across and 4 feet deep.
Nor were the guns accurate. What gunners call the range probable error was plus or minus 1.49 miles at maximum range. The deflection probable error (lateral dispersion) was plus or minus a half-mile. Paris in 1918, with its main administrative districts, was about 7.5 miles across. That meant that while the guns had a fair chance of hitting the city, just where in the city was anybody’s guess. Between March and August the three Paris Guns fired approximately 367 rounds (French records claim 303), but only 183 landed within the city limits. The shells killed 256 Parisians and wounded another 620. The largest casualty count from a single shot happened on the afternoon of Good Friday, March 29, when a round hit the Church of Saint-Gervaiset-Saint-Protais. The explosion and subsequent collapse of the vault killed 88 worshipers and wounded 68.
Since the Paris Guns were essentially modified naval weapons, the Imperial German Navy supplied the crews. About 60 to 80 naval gunners and a support team of civilian engineers manned each gun. The three-gun battery initially operated under the direct command of Vice Adm. Maximilian Rogge, chief of the Imperial German Navy’s Ordnance Department. An army infantry battalion provided ground security for the battery, and 10 squadrons of aircraft were assigned the air cover mission. By 1918 both Allied and German sound-ranging systems were technologically sophisticated enough to pinpoint an enemy battery to within 65 feet, under ideal conditions. Thus the Germans positioned 30 army heavy artillery batteries around the Paris Guns, timing their own firing to mask the firing of the main battery.
Kaiser Wilhelm II personally visited the firing positions on the first day of operations. Despite the initial French confusion and German efforts to keep the guns hidden, by March 24 the French had a general idea where they were. About noon that day the Paris Guns battery started receiving random French counter-fire. Although it was generally inaccurate, one shell hit a tree close to the No. 1 gun, and the resulting air burst wounded a half-dozen crewmen. The following day the No. 3 gun suffered its tube detonation.
The battery displaced forward twice during the war. Its second firing position was near Beaumont-en-Beine, the third near Bruyères-sur-Fère, less than 60 miles from Paris. The re-bored tubes, with reduced ranges due to their larger firing chambers, could only be used in these advance positions.
Despite the impressive tactical gains the Germans made during their 1918 offensives, they were forced to fall back in the face of the Allied counteroffensive that started on July 18. A German crew fired the last round from a Paris Gun on the afternoon of Aug. 9, 1918, after which the weapons were disassembled and taken back to Germany. As war’s end approached, the Germans destroyed the Paris Guns, and Krupp incinerated most of the research and development records. The only remaining evidence of the guns are the concrete firing emplacements in the woods near Crépy.
Though the Paris Guns were an awesome technological achievement they had no impact on the outcome of World War I. But they could have.
The Germans chose to use an advanced technology as a psychological terror weapon, when they could have directed its power against far more militarily significant targets. One of the Allies’ greatest vulnerabilities in 1918 was the fragile and over-stressed logistics system of the British Expeditionary Force. The BEF’s communications lifeline to France ran from just a few key ports in Britain to only six main ports in France. Those ports were vital choke points the Germans, inexplicably, never sought to attack. Had they put the Paris Guns into battery in Flanders instead of Picardy, they easily could have bombarded Dover, England, and Boulogne or Calais, France. As early as 1914 Rausenberger himself told OHL he could build a gun capable of hitting Dover. Any degree of pressure on the BEF’s ports would have caused far greater disruption than any sense of terror among the civilian population in the French capital.
The Germans made the same sort of strategic mistake again in World War II. This time the wonder weapons were the V-1 flying bomb and the V-2 rocket. But again the Germans targeted the population centers of London and Paris versus, say, critical Allied airfields on the continent. Only during the very last days of the war did the Germans start targeting the key Allied port of Antwerp. By 1944 the Germans should have had enough experience from both world wars to know that long-range terror attacks on civilian population centers not only don’t work but also often produce the opposite of the intended effect—a lesson lost on many present-day military and political leaders.
Major General David T. Zabecki, U.S. Army (Ret.), is Weider History Group’s chief military historian. He holds a doctorate in military history from Britain’s Royal Military College of Science, and he is an honorary senior research fellow in war studies at Britain’s University of Birmingham. He is the editor of the recently published four-volume encyclopedia Germany at War: 400 Years of Military History. For further reading Zabecki recommends The Paris Gun, by Henry W. Miller, and Paris Kanonen: The Paris Guns (Wilhelmgeschütze) and Project HARP, by Gerald V. Bull and Charles H. Murphy.
Originally published in the May 2015 issue of Military History. To subscribe, click here.