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Early in October 1202, a fleet of 200 ships set sail from the lagoon of Venice. Banners whipped from every masthead, some bearing the lion of Venice, others charged with the coats of arms of the noblest houses of France.

Leading the fleet was the state galley of Doge Enrico Dandolo, the elected duke of the Venetian Republic. He was more than 80 years old and nearly blind, but undimmed in vigor and ability. His galley was painted imperial vermilion, and a vermilion silk canopy covered the poop deck on which the doge sat in state. In front of him, four silver trumpets sounded, answered from the other ships by hundreds of trumpets, drums and tabors.

The goal of this expedition, this Fourth Crusade, was to win back the holy city of Jerusalem. Conquered by Islamic armies in the 7th century, it had been regained for Christendom by the First Crusade in 1099. In 1187, during the Second Crusade and just 15 years before the doge’s fleet set sail, Jerusalem fell to the Muslim Saladin, who then stalemated a recovery attempt by the Third Crusade (1189-92). The Fourth Crusade was to follow a new strategy: strike at Egypt, the base of Muslim power. But it never reached its goal. Instead, a bizarre twist of fate turned the latest crusaders in a totally unexpected direction—toward the great Christian city, Constantinople, capital of the Byzantine (or Eastern Roman) Empire.

The Fourth Crusade was actually conceived in 1199 at a jousting tournament held by Thibaut, Count of Champagne, at Ecry-sur-Aisne in northern France. There, in a sudden wave of mass emotion, the assembled knights and barons fell to their knees weeping for the captive Holy Land. They swore solemn oaths to go as armed pilgrims to wrest it from the infidels. In the months that followed, the crusade took form in a series of feudal assemblies headed by Count Thibaut; Baldwin, count of Flanders; and Louis, count of Blois. Rather than wear out their army by a long land-march through hostile territory, the leaders decided to reach Egypt by sea. A delegation of six trusted knights went to Venice, the leading seafaring city of Western Europe, to arrange for passage. One of those envoys, Geoffrey of Villehardouin, marshal of Champagne, later wrote a chronicle of the expedition.

In Venice, Villehardouin and his fellow envoys hammered out an agreement with Doge Dandolo and his council. Venice would provide transport ships, crews and a year’s provisions for 4,500 knights with their mounts, 9,000 squires and sergeants (feudal men-at-arms of less than knightly rank), and 20,000 ordinary footmen, for a total of 33,500 men and 4,500 horses.

The price for this armada would be 84,000 marks of silver. And the old doge made Venice not a mere supply contractor, but a full partner in the crusade. In return for a half-share of all conquests, Venice would provide an escort force of 50 fully manned war galleys. The great fleet was to sail in the summer of the next year, 1202.

About that time, a teenage boy escaped from captivity in Constantinople. He was Alexius Angelus, son of the deposed Byzantine Emperor Isaac II. Six years earlier, in 1195, Isaac’s brother—also named Alexius—had overthrown and imprisoned him, taking the throne for himself as Emperor Alexius III. Isaac was blinded, the traditional Byzantine way of dealing with rivals, since by custom a blind man could not be emperor.

Alexius III’s talents did not match his ambition. He made his brother-in-law admiral of the imperial navy. The brother-in-law stripped the fleet bare, selling off gear and entire ships to line his own pockets. The new emperor was also careless in guarding his captives. The blinded Isaac II was no threat, but his son Alexius was able-bodied enough to escape. Eventually he found his way to the court of German King Philip of Swabia, whose queen was the boy’s sister Irene.

In the meantime, there was another fateful event—Thibaut of Champagne died before the crusade could set forth. To take his place as leader, his fellow barons chose a northern Italian nobleman, Count Boniface of Montferrat. Boniface had family ties to the nominal Christian king of Jerusalem, leader of the Christians who still held out in parts of the Holy Land. He also happened to be a vassal of King Philip of Swabia, the same with whom young Prince Alexius had taken refuge. Boniface and the young prince probably met when Boniface visited his liege lord’s court late in 1201.

And now came the seeding of a new plan—the crusaders could stop at Constantinople on their way to Egypt, overthrow the usurper Alexius III and put the young Alexius on the imperial throne.

For 500 years, it may be recalled, the Byzantine Empire had been Christendom’s chief bulwark against the Islamic challenge. By 1201 the empire, though greatly shrunken and weakened, was still the most powerful and best organized of Christian states. But relations between Byzantines and Western Christians had deteriorated steadily through the century of the crusades, over which they were often at odds. From a Western viewpoint, an emperor who owed his throne to crusaders might be more cooperative.

During the late spring of 1202, the crusaders began to gather at Venice. By the intended departure date their host totaled some 10,000 men, far short of the 33,500 planned for—and too few to provide the agreed upon charter fee. The Venetians had suspended their regular commerce to build and equip an immense fleet. Now they demanded that the crusaders hold up their end of the deal: 84,000 marks, or no crusade.

The Fourth Crusade seemed on the point of collapse. Then Doge Dandolo made an offer. The Venetians would suspend the unpaid balance of the transport charge in return for a small consideration—the crusaders’ assistance in conquering the city of Zara (later to become Zadar, Yugoslavia), a Hungarian-owned port on the Dalmatian coast of the Adriatic. To the more pious crusaders, this was a devil’s bargain, an unholy act of war against fellow Christians. But others, including the leading barons, saw no choice if the crusade was to go forward. With some difficulty, they persuaded the dissidents to go along.

At last the fleet could set forth. It included three main ship types. About 40 vessels, called simply ships, were standard Mediterranean heavy cargo ships, two-deckers for the most part, with high fore- and after-castles, twin steering oars and two masts on which triangular lateen sails were hung from long sloping yards. They were slow and unhandy, but their size and height made them effective in defense—or in attack against fixed objectives. Offering mobile support were 60 fighting galleys, rowed not by chained slaves or convicts, but by free and armed Venetian seamen.

The remaining 100 or so ships were uissiers (or huissiers), horse transports. These resembled galleys, but were larger and heavier, with fewer oars. An uissier’s hold was divided into stalls for horses, which were firmly strapped into place when the vessel was underway. A door-like hatch over an entry port in the hull aft could be lowered, drawbridge-fashion, to lead the horses in and out of the hold. These medieval counterparts to the LST (landing ship, tank) allowed knights to go ashore ready for immediate action.

On November 10, the fleet reached Zara, which surrendered after a 14-day siege. Many knights deserted rather than take part. (One was Simon de Montfort, whose son, also named Simon de Montfort, later won fame in England as the father of Parliament. The elder Simon’s moral scruples about crusading against Christians were short-lived, for it was he who later led the brutal Albigensian crusade, which ravaged much of southern France in the name of stamping out heresy.) After Zara, meanwhile, Pope Innocent III excommunicated the Venetians and threatened to excommunicate the entire crusade.

The crusaders set up winter quarters at Zara, as it was too late in the season to go on. There, the leaders met with Prince Alexius and agreed to put him on the Byzantine throne in place of Alexius III. The usurper was hated in Constantinople, Prince Alexius assured them. In return for the crusaders’ aid, he promised to pay off their debt to the Venetians and lead a Byzantine army in the proposed assault on Egypt.

In the spring of 1203, the crusade set out from Zara. And then an odd incident took place as the fleet rounded the southern tip of Greece. The crusaders passed passed two ships carrying knights and men-at-arms—who hid their faces in shame when the ships were hailed and boarded. They had never joined the main crusading force at Venice, but had sailed to the Holy Land on their own from another port. The errant knights had accomplished nothing and suffered heavily from the plague before giving up. According to Villehardouin, one now deserted in reverse.

Do what you like with anything I’ve left behind, he told his comrades, I’m going with these people, for it certainly seems to me they’ll win some land for themselves! And with that less-than-pious remark, he jumped into the boat with the departing boarding party and joined the fleet.

On June 24, 1203, the fleet passed in review beneath the walls of Constantinople. The crusaders landed on the Asian side of the Bosporus and—following a skirmish ashore—set up a base at the city of Scutari, just a mile across the Bosporus from Constantinople. On July 3, at Dandolo’s suggestion, they tried to trigger a popular rising in young Alexius’ favor. Alexius stood dressed in state robes on the poop of a galley that rowed back and forth under the walls of the city to display their rightful emperor to the people. The response was less than overwhelming. When the galley came close to the walls it was met by a hail of arrows, not by the hoped-for cheers.

That episode was fair warning for the crusaders’ leaders, who, especially wily old Dandolo, have been accused of cynically plotting the conquest of Constantinople for their own profit. If Dandolo and the other leaders sincerely believed in Prince Alexius as their vehicle, their belief was wrong. A Byzantine emperor was not a dynastic king like those of the feudal West. In the Roman imperial tradition, he was more a president for life with absolute authority. Whoever could take the throne and hold it was accepted as emperor. But young Alexius had no special right to the throne simply because he was the son of a deposed former emperor—and, whatever the Byzantines thought of their present emperor, they would not take a new one at the hands of foreigners.

Losing hope of a popular uprising, the crusaders then settled down to the serious matter at hand. The city of Constantinople (today’s Istanbul, Turkey) was roughly triangular, set on a peninsula between the Sea of Marmara on the south and the Golden Horn, the city’s great harbor, on the north. Only to the west could it be attacked by land—and the land walls were one of the world’s greatest fortifications. Built 800 years earlier by the Roman Emperor Theodosius the Great, they consisted of a moat backed up by a parapet, and behind that a double wall. Less elaborate single walls protected the city along the Marmara shore and the Golden Horn harbor front. The Golden Horn was guarded by a chain across the harbor entrance, and the far end of the chain was covered in turn by a fortress called the Tower of Galata.

Armies far mightier than the crusaders had dashed themselves to ruin before those defenses. Constantinople withstood two epic sieges by the Muslim Arabs, from 673 to 678 and in 717, and other sieges by Avars, Bulgars and Russian Vikings. Manning its walls were the hard core of the Byzantine army, the feared ax-wielding Varangian Guard. First recruited from Vikings, the Varangian Guard became heavily Anglo-Saxon in the years after the Norman conquest of England. Aiding the defense were Pisans, bitter trading rivals of the Venetians.

The city’s first line of defense normally would have been the dromons, Byzantium’s great double-banked galleys. But the graft of the emperor’s brother-in-law had reduced the fleet to 20 old and useless ships. The Byzantines could only take defensive positions and wait for the blow to land. It came on July 5. The crusaders crossed the Bosporus, landing near the Tower of Galata. A few dromons could have intervened with decisive effect at this point, but no Byzantine ships were fit for action.

Emperor Alexius III led a large field army out to oppose the landing. Crusader horse-transports ran onto the beach, supported by crossbow and archery fire, and dropped their entry-port covers as ramps. Down rode armored French knights, lances couched. A century earlier, the Byzantine princess and historian Anna Comnena had written that a French knight’s charge would make a hole through the walls of Babylon. The Byzantines retreated, abandoning tents and booty to the crusaders.

The Tower of Galata was now open to attack. Its English, Danish and Pisan garrison mounted an active defense, making sallies against the invaders. In one such action the defenders were forced back and could not shut the gates of the tower before the advancing French. It fell by storm. A giant Venetian transport, Aquila (Eagle), charged the harbor chain under full sail and snapped it. Venetian galleys rowed into the harbor, quickly disposing of the weak Byzantine squadron drawn up behind the chain. The crusaders then took up quarters in the unwalled suburbs of Pera and Estanor on the north side of the Golden Horn. Their leaders met to plan their attack on the city itself.

Doge Dandolo recommended an attack on the harbor wall. It was less formidable than the land walls, and the big transports could nudge close to serve as floating siege towers. The French, however, wanted to fight ashore, in their own element. The final decision was to mount a double attack, the Venetians against the harbor wall and the French against the north end of the land wall, adjacent to the Palace of Blachernae. This section of wall was a late addition and somewhat weaker than the original Theodosian land walls. After crossing the Golden Horn, the French took up a position opposite the wall, near a fortified monastery they called Bohemond’s Castle after a hero of the First Crusade.

The double assault was launched on July 17. The Venetian fleet formed up in line and advanced against the harbor wall. The big transports raised flying assault bridges, fashioned from spars and suspended from their foremasts, an arrangement that allowed men on the bridgeheads to fight, three abreast, from positions equal in height to the tops of the towers they were assaulting. Fire support was provided by mangonels and petraries, catapult-like mechanical artillery set up aboard the ships. Light and speedy by comparison, the maneuverable galleys were ready to throw reinforcements ashore where needed.

The attack hung in the balance until Doge Dandolo ordered his own galley to advance and set him ashore. The courage of the old doge fired up the Venetians, and they pressed home the attack. The Venetian banner was hoisted atop a wall tower. Soon 25 towers—about a mile of wall—were taken.

Behind the wall, however, the Varangian guardsmen held their ground. Unable to advance, the Venetians set fire to nearby buildings. Driven by the wind, the fire then burned much of the city. The Venetians also captured a few horses on the waterfront, and with some irony, as one naval historian put it, sent them around to the French knights.

The French attack on the land wall did not go so well. Scaling ladders were less effective than the Venetians’ floating siege towers, and the assault was thrown back. Emperor Alexius III took to the field in a counterattack, leading an imperial force of nine battles, or massed formations, out the gates. The French met it with seven battles of their own.

As often happened with feudal armies, the logic of command and control conflicted with the chivalric impulse to be first in the attack. Count Baldwin, in command of the leading battle, at first held his ground, but other crusaders went brashly forward—forcing Baldwin to follow, to save face—until they all found themselves dangerously exposed to the Byzantine army and out of sight of most of their own force.

Word of the French peril reached Doge Dandolo. Saying he would live or die with the crusaders, he ordered his men to abandon their hard-won towers and redeploy in support of their allies. And at the sight of Venetian galleys moving up the harbor to set more troops ashore, the emperor retreated into the city. He had achieved his tactical objective, holding off the French and forcing the Venetians to abandon their gains.

But Alexius III also had lost his nerve. That night he fled the city with his mistress and a favorite daughter — leaving his empress behind. Byzantine nobles hastily met and restored blinded old Isaac II, young Alexius’ father, in disregard of the tradition that made blindness a bar to the throne. When the crusaders heard of this, they demanded that young Alexius be crowned alongside his father. They still had a powerful army and fleet, they had nearly taken the city, and there was no real leadership among the defenders. The demand was granted, and young Alexius was escorted into the city in state, along with the doge and the leading French counts and barons.

The crusaders’ assault had failed tactically, but it had won its strategic objective. The late emperor, Alexius III, was a fugitive, and young Alexius now sat crowned beside his father as Emperor Alexius IV. And next? It was too late in the season to go on, but the crusaders looked forward to receiving supplies and Byzantine reinforcements. Come spring they could sail on to Egypt and restore the Holy Land to the Cross.

Alas, young Alexius could not keep the grand promises he had made. The imperial treasury was empty. Moreover, while the Byzantines and the crusaders were now allies in theory, their relationship was actually poor and grew steadily worse. The Byzantines detested the crudity of the French and the highhandedness of the Venetians. In turn, the Westerners despised the Byzantines as effete cowards.

After repeated riots, one of which led to a second disastrous fire, individual crusaders no longer dared show themselves in the city. Moreover, Byzantine hatred of the barbarians extended beyond the crusaders to embrace all the Western Europeans who lived in the city — even the Pisans who had fought recently and well on the Byzantine side. Men, women and children were massacred. The survivors fled to the crusader camp, considerably reinforcing the invaders’ army.

Young Alexius IV could not raise enough money to satisfy the crusaders, nor could he force them away. He fell under the influence of a noble adviser, Alexius Ducas, popularly known as Mourtzouphlos, a name that referred to his prominent, bushy eyebrows. Eventually, Mourtzouphlos did a typically Byzantine thing — he lured the young emperor into a trap, kidnapped and imprisoned him, and took the throne for himself.

Mourtzouphlos, now Emperor Alexius V (the third Emperor Alexius in one year!), was more of a leader than his recent predecessors. He slammed shut the gates of the city against the crusaders and put the defenses in order. Wooden superstructures were built atop the towers of the harbor wall, raising them two or three stories and reducing the effectiveness of the Venetian ships as floating siege towers. Gates in the wall were bricked up to eliminate weak spots in the defenses.

Mourtzouphlos also took active outreach measures. The crusader fleet was moored in the Golden Horn, directly across from the city. One December night when the wind blew from the south, he launched a fireship attack against the Venetian fleet. It was a textbook situation — in the confined anchorage, against a lee shore, the Venetians could not simply drop back and let the fireships burn out.

But they were not rattled. They manned their galleys, drove off boatloads of archers covering the fire attack, grappled the fireships and towed them clear of the fleet. According to Villehardouin, No men ever defended themselves more gallantly on the sea than the Venetians did that night.

In January, Mourtzouphlos received word that a crusader foraging expedition was raiding the town of Philia, some miles northwest of Constantinople. He ambushed the returning crusaders, but the cornered and outnumbered French knights rallied to the counterattack. They drove off the Byzantines and captured the imperial standard and the holy icon that traditionally accompanied Byzantine emperors into battle.

Mourtzouphlos nonetheless returned to Constantinople and proclaimed a victory. Asked about the standard and icon, he claimed that they were put away in safekeeping. Word of this lie quickly reached the crusaders, who did the logical thing: they mounted standard and icon on a Venetian galley and paraded them back and forth under the harbor walls. That affair was fatal to the unfortunate prisoner Alexius IV. Mourtzouphlos, humiliated, feared a palace revolt in the young deposed emperor’s name. After several efforts at poisoning failed, Mourtzouphlos had him strangled. Old Isaac II died about the same time, probably without need of assistance.

The crusaders saw they could not hope to have the cooperation of any Byzantine emperor. They resolved instead to conquer the city and take the entire Byzantine Empire for themselves. Six French and six Venetian nobles were to elect a new emperor, who would receive a quarter of the empire in his own name, the rest being divided between French feudal fiefs and Venetian holdings. Doge Dandolo—who had gradually emerged as the real leader of the crusade—saw to it that the Venetians owed no feudal duties for their quarter and a half (that is, three-eighths) of the Empire.

In the previous assault, the Venetians had succeeded against the harbor wall, so the French leaders were persuaded to join them in another amphibious attempt. Knights and horses embarked in the horse transports; others boarded the assault ships. As armor protection against Byzantine mechanical artillery, the ships were protected by wooden mantlets, which were covered with vines, to soften impacts, and vinegar-soaked leather as protection against incendiary Greek fire.

On the morning of April 9, 1204, the fleet moved forward against the harbor wall to the sound of trumpets, drums and tabors, with flags and pennants flying. But a south wind made it difficult to close with the shore, and only the largest ships carried structures high enough to match Mourtzouphlos’ new defenses. Men on the bridges traded indecisive strokes with the ax-wielding Varangians in the towers. Other crusaders landed below the walls. Under cover of defensive shells called turtles, they attempted to break through the bricked-up gates.

To no avail. After several hours and no success, the crusaders were forced back, and the fleet retired. They had lost about 100 dead, while Byzantine losses were few. According to Robert de Clari, a knight who wrote an eyewitness account, some defenders added insult to injury. They dropped their breechclouts and displayed bare buttocks to the retreating crusaders.

Mourtzouphlos had personally directed the defense from high ground behind the harbor wall, near the monastery of Christ Pantopoptes, the All-Seeing. Now he proclaimed success to his people. “Am I not a good Emperor?” he asked them, and answered his own question: “I am the best Emperor you have ever had. I will dishonor and hang them all.”

A weary and dispirited group of crusading leaders met that evening to plan their next move. Some of the French suggested an attack on the Sea of Marmara side of the city, where the defenses had not been reinforced. Doge Dandolo explained that this was not practical, as the currents and prevailing winds would interfere with an assault there.

The final decision was for another attempt on the harbor wall, with one important innovation. The big transports were lashed together in pairs, allowing two ships’ bridges and assault groups to concentrate against each tower.

The assault was planned for Monday, April 12. On Sunday, all the crusaders, including the excommunicated Venetians, celebrated Mass. To allow greater concentration on the task at hand, according to Robert de Clari, all the prostitutes accompanying the crusading army were bustled onto a ship and sent far away.

On Monday the fleet attacked, aided this time by a favoring wind. But the previous setback had raised the defenders’ spirits, and the walls and towers were heavily manned. For hours the fighting was indecisive. Then a gust of wind pushed two of the largest ships, Peregrino (Pilgrim) and Paradiso, hard up against the foreshore.

An assault bridge made contact with the top level of a tower, and a Venetian scrambled onto it, only to be cut down. Then a French knight named André d’Ureboise made it across and stood his ground. (He must have been a man of exceptional skill and valor to be able to fight fully armored high above a swaying ship). Reinforcements joined d’Ureboise, and the Varangian defenders were forced out of the tower. Within minutes, five towers fell to the attackers. The action now turned to the base of the wall. A group of men with picks broke through a bricked-up gate. A warlike priest — Robert de Clari’s brother Aleaumes—crawled through the hole and drove back the defenders on the other side. A handful of knights climbed through after him.

That breakthrough took place right below Mourtzouphlos’ command post. The emperor spurred forward to counterattack. The crusaders stood their ground, and he retreated. For him, and for Byzantium, it was a fatal loss of nerve. Other gates were broken open, and war horses swarmed out of the transports and into the city. The crusader knights formed up for a mounted charge. The Byzantine defensive formation broke, and the emperor himself fled into one of his palaces.

The corner had been turned, but the crusaders were worn out by the day’s fighting and still outnumbered. They expected weeks of street-by-street fighting to come, and took up a defensive position along the wall, torched nearby buildings—the siege’s third fire—to protect themselves against a counterattack in the night.

During the night, Alexius Mourtzouphlos Ducas fled, just as Alexius III had the previous fall. Resistance ceased.

For the next three days, this greatest of Christian cities suffered a thorough and ruthless sack. Priceless treasures of antiquity were smashed to pieces or melted down for their precious metals. While the French knights and men-at-arms went on a drunken rampage, the Venetians set to work like seasoned professional thieves, scooping up the best of the fallen city’s treasures. The four great bronze horses that now grace the front of St. Mark’s in Venice are only the most notable monuments to the thoroughness of their rapacity.

The Byzantine Empire never recovered. The Latin Empire that the crusaders set up in its place was a shaky affair that never gained control of much former Byzantine territory. Boniface of Montferrat, the crusade’s nominal leader, was pushed aside, and Baldwin of Flanders became Emperor Baldwin I. The next year he was taken prisoner in an ill-advised battle. Soon the Empire was reduced to little more than the city of Constantinople, and in 1262 it was retaken by a Byzantine emperor-in-exile, Michael Paleologus. But the restored Byzantium never regained its former power and was finally and forever extinguished by the Turks in 1453.

As a military operation, the Fourth Crusade stands out as one of history’s great amphibious assaults. Twice the harbor wall of Constantinople fell to direct assault from the ships of the Venetian fleet. In most land sieges, deploying just one siege tower was a major effort. The Venetian fleet had deployed an entire line of them!

During the later age of men-of-war armed with cannon, this newborn amphibious capability was lost. Successful amphibious assaults were rare during the age of fighting sail. Even in World War I, when the Allies unsuccessfully attacked Gallipoli (prelude to an intended assault on Constantinople), soldiers were condemned to flounder ashore in ships’ boats ineffectually supported by warships. Not until World War II did amphibious warfare again reach the level of sophistication embodied in the Venetian fleet during the Fourth Crusade.

This article was written by Richard McCaffery Robinson and originally appeared in the August 1993 issue of Military History magazine.

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