In the years from 1201 to 1202 the Fourth Crusade, sanctioned by pope Innocent III, was readying itself to set out to conquer Egypt, which was by then the center of Islamic power.
After initial problems, finally Boniface, the Marquis of Monferrat was decided as the leader of the campaign.
But right from the beginning the Crusade was beset by fundamental problems. The main problem was that of transport. To carry a crusading army of tens of thousands to Egypt a substantial fleet was required.
And as the Crusaders were all from western Europe, a western port would be required for them to embark from.
Hence the ideal choice for the Crusaders seemed to be the city of Venice. A rising power in the trade across the Mediterranean, Venice appeared to be the place where enough ships could be built in order to carry the army on its way.
Agreements were made with the leader of the city of Venice, the so-called Doge, Enrico Dandolo, that the Venetian fleet would transport the army at the cost of 5 marks per horse and 2 marks per man.
Venice was therefore to supply a fleet to carry 4'000 knights, 9'000 squires and 20'000 foot soldiers to 'recapture Jerusalem' for the price of 86'000 marks.
The destination might have been worded as Jerusalem, yet from the outset the goal was clearly seen as the conquest of Egypt by the leaders of the Crusade.
Egypt was weakened by a civil war and its famous port of Alexandria promised to make it easy to supply and reinforce any western army. Also Egypt's access to both the Mediterranean Sea as well as the Indian Ocean meant it was rich in trade.
The fleet built with the money should remain in Venetian hands after it had safely dispatched the crusaders to the east.
As a their contribution to the 'holy' efforts of the Crusade the Venetians further agreed to provide fifty armed war galleys as an escort to the fleet. But as a condition of this they shoudl receive half of any conquest that should be made by the Crusaders.
The conditions were steep, and yet no where else in Europe could the Crusaders hope to find a seafaring power capable of shipping them to Egypt.

However, things were not to go according to plan. There was considerable distrust and animosity amongst the crusaders. This led some of them to instead make their own way to teh east, finding their own means of transportation.
John of Nesle reached Acre with a force of Flemish fighters in 1202 without the Venetian fleet. Others made their sea voyage eastward independently from the port of Marseilles.
With many of the fighters therefore not arriving in Venice, the leaders soon realized that they would not reach the expected number of troops. But the Venetians were already building the fleet to the agreed size.
The individual knights had been expected to pay their fare when they arrived. As many had now travelled independently, this money was not forthcoming to the leaders in Venice.
Inevitably, they could not pay the sum of 86'000 marks they had agree with the Doge.
Worse still, they were encamped at Venice on the small island of St. Nicholas. Surrounded by water, cut off from the world, they were not in a strong bargaining position.
As the Venetians finally demanded they should pay the promised money, they tried their best to collect whatever they could, but still remained 34'000 marks short.
The knights, naturally bound by their strict code of honour, now found themselves in a terrible dilemma. They had broken their word toward the Venetians and owed them an enormous sum of money.
Doge Dandolo however knew how to play this to his utmost advantage. It is generally assumed that he had foreseen the shortfall in numbers of the crusaders early on and yet still he had pressed on with the shipbuilding. Many suspect that he right from teh start endeavoured to snare the crusaders into this trap.He had achieved his ambition. And now his plans should begin to unfold.

Venice had been deprived of the city of Zara by the Hungarians who had conquered it. Not only was this a loss in itself, but it also was a potential rival to their ambition of dominating the trade of the Mediterranean. And yet, Venice didn't possess the army it required to re-conquer this city.
Now however, with the massive crusading army indebted to it, Venice suddenly had found such a force.
And so the crusaders were presented with the Doge's plan, that they should be carried to Zara by the Venetian fleet, which they should conquer for Venice. Any spoils thereafter would be shared between the crusaders and teh Venetian republic.
The crusaders had little choice. For one they owed money and saw any loot they should capture in Zara as the only means of repaying their debt. On the other hand they well know that, if they should not agree with the Doge's plan, then supplies such as food and water would suddenly fail to arrive which which to feed their army on their little island off Venice.
Zara was a Christian city in the hands of the Christian King of Hungary. How could the Holy Crusade be turned against it ?
But want it or not, the crusaders had to agree. They had no choice.
Papal protestations were made; any man to attack Zara would be excommunicated. But nothing could stop the impossible from happening, as the Crusade as hi-jacked by Venice.
In October 1202 480 ships left Venice carrying the crusaders to the city of Zara. With some stops in between it arrived on 11 November 1202.
The city of Zara stood no chance. It fell on 24 November after five days of fighting. Thereafter it was thoroughly sacked. In an unimaginable twist of history the Christian crusaders were ransacking Christian churches, stealing everything of value.
Pope Innocent III was furious, and excommunicated every man who had taken part in the atrocity.
The army now passed the winter in Zara.
Message was sent by the crusaders to pope Innocent III, explaining how their dilemma had forced them to act in service of the Venetians. In consequence the pope, hoping that the Crusade might now resume its original plan of attacking the forces of Islam in the east, agreed to restore them to the Christian church and hence annulled his recent excommunication.

Meanwhile the situation of the crusaders had not much improved. That half of the loot which they had made with the sack of Zara still was not enough to repay the outstanding debt of 34'000 marks to the Venetians. In fact, most of their spoils was spent on buying food for themselves throughout their winter stay in the conquered city.
Now whilst the army had been in Zara, its leader, Boniface, had passed Christmas in far away Germany at the court of the king of Swabia.
Philip of Swabia was married to Irene Angelina, the daughter of emperor Isaac II of Constantinople who had been overthrown by Alexius III in 1195.
The son of Isaac II, Alexius Angelus, had managed to flee Constantinople and make his way, via Sicily, to the court of Philip of Swabia. It is generally understood that the powerful Philip of Swabia, who was confidently awaiting the title of Emperor of the Holy Roman Empire to be bestowed upon him sooner or later, had ambitions to divert the Crusade toward Constantinople to install Alexius IV on the throne in place of the current usurper.
If the leader of the Crusade, Boniface of Monferrat, visited at such a vital time, it was most likely in order to discuss the Crusade. And it is therefore well likely that he came to know of Philip's ambitions for the campaign and most likely supported them. In any case, Boniface and the young Alexius appeared to leave Philip's court together.
Doge Dandolo also had his reasons for wanting to see the Crusade's planned attack on Egypt diverted. For in the spring of 1202, behind the back of the crusaders, Venice negotiated a trade agreement with al-Adil, the Sultan of Egypt. This deal granted the Venetians enormous privileges of trade with the Egyptians and therefore with the trade route of the Red Sea to India.
Also, the ancient city of Constantinople was the main obstacle to prevent Venice from rising to dominate the trade of the Mediterranean Sea. But furthermore there seemed to have been a personal reason for which Dandolo wanted to see Constantinople fall. For it was during his stay in the ancient city that he had lost his eyesight. If this loss came about by illness, accident or other means is unknown. But Dandolo appeared to hold a grudge.
And so it was that the embittered Doge Dandolo and the desperate Boniface now hatched a plan by which they could redirect the Crusade to Constantinople.
The pawn in their schemes was the young Alexius Angelus (Alexius IV) who promised to pay them 200'000 marks if they would install him on the throne of Constantinople. Also Alexius promised to provide an army of 10'000 men to the Crusade, once he was on the throne of the Byzantine empire.
The desperate crusaders needed not be made such an offer twice. At once they agreed to the plan.
As a excuse for such an attack on what was the greatest Christian city of its day, the crusaders sited that they would act to restore the eastern Christian empire to Rome, crushing the Orthodox church which the pope deemed a heresy.
On 4 May 1202 the fleet left Zara. It was a lengthy journey with many stops and distractions and the odd looting of a city or island in Greece.

But by 23 June 1203 the fleet, consisting of roughly 450 large ships and many other small ones, arrived off Constantinople.
Would Constantinople now have possessed a powerful fleet, it could have given battle and perhaps defeated the invaders. Instead however, bad government had seen the fleet decay over years. Lying idle and useless, teh Byzantine fleet wallowed in the protected bay of the Golden Horn. All that protected it from the menacing Venetian war galleys was a great chain which spanned across the entrance to the bay and hence made any entry by unwelcome shipping impossible.
Meeting no challenge the crusaders took to the eastern shore. Resistance was impossible. In any case, there was none against this horde of thousands which poured on to the eastern shore of the Bosporus. The city of Chalcedon was captured and the leaders of teh Crusade took up residence in the emperor's summer palaces.
Two days later, having plundered Chalcedon for all it was worth, the fleet then moved a mile or two north where it set upon the harbour of Chrysopolis. Once again, the leaders resided in imperial splendour while their army ransacked the city and everything around it.
The people of Constantinople were no doubt shaken by all these occurrences. After all, no war had been declared on them. A trop of 500 cavalrymen were sent to scout out just what was going on amongst this army which to all accounts seemed to have gone berserk.
But no sooner did this cavalry come close it was charge at by mounted knights and fled.
Though one must add that the cavalrymen and their leader, Michael Stryphnos, hardly distinguished themselves that day. Was their force one of 500, the attacking knights were a mere 80.
Next an ambassador, a Lombard named Nicholas Roux was despatched from Constantinople across the water to find out just what was going on.
It was now that it was made plain to the court of Constantinople that this Crusade had not stopped here to continue onwards to the east, but to place Alexius IV on the throne of the eastern empire. This message was followed up by a farcical display the next day, when the 'new emperor' was presented to the people of Constantinople from a ship.
Not only was the ship forced to stay out of reach of the catapults of the city, but so too was it pelted with abuse from those citizens who took to the walls in order to give the pretender and his invaders a piece of their mind.

On 5 July 1203 the fleet carried the crusaders across the Bosporus to Galata, the stretch of land lying north of teh Golden Horn. Here the coast was far less sternly fortified than around Constantinople and it was host to the Jewish quarters of the city.
But all this was of no importance to the crusaders. Only one thing mattered to them Tower of Galata. This tower was a small castle which control one end of the chain which barred the entrance to the Golden Horn. This was their goal.
Had the Byzantines tried to put up soem resistance against the landing of the crusaders it was simply wiped aside and sent the defenders fleeing.
Now the crusaders evidently hoped to lay siege to the tower or take it by storm within the following days.
However, with the Tower of Galata and the entrance to the Horn in danger, the Byzantines tried once more to challenge the western knights in battle and drive them off the shore. On 6 July their troops were ferried across the Golden Horn to join the garrison of the tower. Then they charged. But it was an insane effort. The small force was dealing with an army 20'000 strong. Within minutes they were thrown back and drive back to their keep. Worse still, in the ferocity of the fighting, they failed to close the gates and so the crusaders forced their way in and either slaughtered or captured the garrison.
Now in control of the Tower of Galata, the crusaders lowered the chain barring the harbour and the powerful Venetian fleet made its way into the Horn and either captured or sunk the ships within it.

Now the great force prepared for their assault on Constantinople itself. The crusaders set up camp out of catapult range at the northern end of the great walls of Constantinople. The Venetians meanwhile built ingenious giant drawbridges along which three men alongside each other could climb from the deck of their ships up to the top of the walls if the ships closed enough on the city's seaward walls.
On 17 July 1203 the first assault of Constantinople took place. The fighting was fierce and the Venetians took parts the walls for some tie but were eventually driven off. Meanwhile the crusaders received a mauling by the emperor's famous Varangian Guard as they tried to storm the walls.
But next the unbelievable happened and emperor Alexius III fled Constantinople on a ship. Abandoning his city, his empire, his followers, his wife and children, Alexius III took flight on the night from 17 to 18 July 1203, taking with him only his favourite daughter Irene, a few members of his court and 10'000 pieces of gold and some priceless jewels.

The next day the two sides awoke to the realization that the reason for the quarrels had disappeared. But the Byzantines, having the advantage of learning of this news first, took the first step in releasing Isaac II from the dungeon of Blachernae palace and restoring him as emperor at once. So, no sooner did the crusaders learn of the flight of Alexius III, then they learnt of the restoration of Isaac II.
Their pretender Alexius IV was still not on the throne. After all their efforts, they still had no money with which to repay the Venetians.
Once more the Fourth Crusade found itself at the brink of ruin. A group was soon arranged to go and negotiate with the Byzantine court and its new emperor, to demand that he, Isaac II, now should fulfill the promises made by his son Alexius.
Alexius now suddenly was in the role of a hostage. Emperor Isaac II, only back on his throne for a few hours, was confronted with the crusader's demands for 200'000 silver marks, a years provisions for the army, the promised 10'000 troops and the services of the Byzantine fleet to carry them to Egypt. The most grave point though was the religious promises Alexius had so rashly made in his efforts to win the favour of the crusaders. For he had promised to restore Constantinople and its empire to the papacy, overturning the Christian Orthodox church.
If only to save his son, Isaac II agreed to the demands and the negotiators of the crusaders left with a document with the golden sea of the emperor on it and went back to their camp. By 19 July Alexius was back with his father at the court of Constantinople.
Yet their was few means by which the emperor coudl actually fulfill the promises he had been forced to make. The recent disastrous rule of Alexius III had, alike many of the previous reigns, virtually bankrupt the state.
If the emperor had no money then any demand to change the religious allegiances of the city and its territories, seemed even more impossible.
Emperor Isaac II well understood that what he now needed most of all was time.
As a first step he managed to convince the Crusaders and teh Venetians to move their camp to the opposite side of the Golden Horn, 'in order to prevent trouble breaking out between them and the citizens'.

The crusaders however, together with some of the advisors of the court, also managed to persuade Isaac II to allow for his son Alexius to be crowned as co-emperor. For one the crusaders wanted at last to see their puppet emperor on the throne. But also the courtiers thought it unwise to have a blind man like Isaac II on the throne on his own.
On 1 August 1203 Isaac II and Alexius VI were formally crowned in the Santa Sophia.
This done the younger emperor now began to see to it that the moneys he had promised were handed to the menacing army to the north. Did the court not possess 200'000 marks, it set about melting down whatever it could in order to make up the debt. In the desperate efforts to somehow make up this massive amount, the churches were stripped of their treasures.
Alexius VI was of course highly unpopular among the people of Constantinople. Not only were they forced to pay huge sums for the privilege of having the unwelcome crusaders forcing him onto the throne, but he also was known to be partying with these western barbarians. Such was the hatred against Alexius IV that he asked the crusaders to stay until March to help him establish himself in power, or else he feared he might be overthrown no sooner had they left. For this favour he promised the crusaders and the fleet yet more money. Without much ado, they agreed.
During some of the winter months Alexius IV then toured the territory of Thrace in order to assure their allegiance and help enforce the collection of much of the money which was needed to pay off the crusaders. To protect the young emperor, as well as to assure he wouldn't cease being their puppet, a part of the crusading army accompanied him.

In Alexius IV absence a disaster struck the great city of Constantinople. A few drunken crusaders, started attacking a Saracen mosque and the people praying within it. Many Byzantine citizens came to the help of the beleaguered Saracens. Meanwhile many of the Italian residents of the merchants quarters rushed to the aid of the crusaders once the violence spiralled out of control.
In all this chaos a fire broke out. It spread very quickly and soon great tracts of the city stood in flames. It lasted for eight days, killing hundreds and destroying a strip three miles wide running right through the middle of the ancient city.
A number as high as 15'000 Venetian, Pisan, Frankish or Genoese refugees fled across the Golden Horn, seeking to escape the wrath of the enraged Byzantines.
It was to this grave crisis that Alexius IV returned from his Thracian expedition. The blind Isaac II by this time had been almost completely sidelined and spent most of his time seeking spiritual fulfillment in the presence of monks and astrologers. The government hence now lay completely in the hands of Alexius IV. And still the overwhelming burden of debt hung over Constantinople, alas the point had been reached where Constantinople reached the point where it either could no longer or simply would no longer pay. Soon after this news reached the crusaders, they began looting the countryside.
Another deputation was sent to the court of Constantinople, this time demanding that the payments be resumed. The meeting was somewhat of a diplomatic disaster. Was its aim to prevent any hostilities from taking place, it instead only inflamed the situation even more. For to threaten the emperor and make demands at his own court was understood as the ultimate insult by the Byzantines.
Open war now broke out again between the two sides.
On the night of 1 January 1204 the Byzantines made their first attack on their opponent. Seventeen ships were filled with flammables, set alight and directed at the Venetian fleet lying at anchor in the Golden Horn. But the Venetian fleet acted swiftly and decisively in avoiding the flaming vessels sent to destroy them and lost only one single merchant ship.

The defeat of this attempt of destroying the Venetian fleet only further increased the ill feeling of the people of Constantinople towards their emperor. Riots broke out and the city was thrown into a state of near anarchy. At last the senate and many of the courtiers decided that a new leader, who could command the trust of the people, was urgently needed. The all convened in the Santa Sophia and debated just whom they should elect for this purpose.
After three days of deliberation a young nobleman called Nicholas Canobus was decided upon, much against his will.
Alexius IV, despairing at these meetings at the Santa Sophia to depose him, sent message to Boniface and his crusaders imploring him to come to his aid.
This was the very moment the influential courtier Alexius Ducas (nicknamed Murtzuphlus for his meeting eyebrows), son of the previous emperor Alexius III, had been waiting for. He told the emperor's bodyguard, the famous Varangian Guard, that a mob was setting towards the palace to kill the emperor and that they needed to bar their entry to the palace.
With the Varangians out of the way, he next convinced the emperor to flee. And no sooner was Alexius III stealing through the streets of Constantinople then Murtzuphlus and his co-conspirators set upon him, ceased his imperial robes, put him in chains and thrown in a dungeon.
Meanwhile Alexius Ducas was hailed emperor by his followers.
Hearing of this news, the senators at the Santa Sophia immediately abandoned the idea of their reluctant chosen leader Nicholas Canobus and instead decided to back the new usurper.
So, with the happening of one night, the ancient city of Constantinople had seen the reign of of the co-emperors Isaac II and Alexius IV come to end, a reluctant nobleman called Nicholas Canobus elected for a matter of hours, before Alexius Ducas alas was recognized after usurping the throne for himself.

The usurper was crowned emperor at the Santa Sophia by the patriarch of Constantinople. The blind and enfeebled Isaac II died of sheer grief and the unfortunate Alexius IV was strangled on the orders of new emperor.
If the new emperor Alexius V Ducas had achieved his power by questionable means, he was a man of action who tried his best arm Constantinople against the crusaders. Immediately he set up work gangs to strengthen and increase in height the walls and towers facing the Golden Horn. He also led cavalry ambushes against those of the crusaders who strayed too far from their camp in search of food or wood.
The ordinary people soon took to him. For it was obvious to them that they stood he best chance of a successful defence against the invaders under his rule.
However the nobility of Constantinople remained hostile to him. This perhaps largely due to the emperor having exchanged all the members of his court against new people. This had cleared away much of the intrigue and possibility of betrayal, but it had also robbed many of the noble families of their influence at court.
Importantly, the Varangian Guard backed the new emperor. Once they had learnt that Alexius IV had sought help from the crusaders and may well have warned them about the attack on the Venetian fleet by the fire ships, they has little sympathy for the overthrown emperor. Also they liked what they saw in the energetic new ruler who was at last taking the fight to the crusaders.

In the camp of the crusaders the leadership may still have theoretically rested in the hands of Boniface, but in practice in now almost lay completely with the Venetian Doge, Enrico Dandolo.
Spring was setting in by now and news was reaching them from Syria that those crusaders who had left independently for Syria at the outset of the campaign, had all either died or had been slaughtered by the Saracen armies.
Their desire for heading to Egypt was getting less and less. And still the crusaders owed the Venetians money. Still they could simply be abandoned by the Venetian fleet in this hostile part of the world, without any hope of aid arriving.
Under Doge Dandolo's leadership it was decided that the next assault on the city should be conducted entirely from the sea. The first attack had shown that the defences were vulnerable, whilst the attack from the landward side had easily been repulsed.
In order to increase the chances of the attacks against the fearsome defensive towers succeeding, teh Venetians lashed pairs of ships together, so creating on single fighting platform, from which two drawbridges simultaneously could be brought to bear on one tower.
However, the recent work by the Byzantines had increased the heights of the towers, making it almost impossible for the drawbridges to reach the top of them.
And yet, there could be no turning back for the invaders, they simply had to attack. Their food supplies would not last forever.
Tightly packed into the ships, on 9 April 1204 the Venetians and Crusaders together set across the golden Horn towards the defences.
As the fleet arrived the crusaders began to drag their siege engines onto the muddy flats immediately in front of the walls. But they stood no chance. The Byzantine catapults smashed them to pieces and then turned on the ships. The attackers were forced to retreat.

The Venetians spent the next two days repairing their damaged ships and readying themselves, together with the crusaders, for the next assault.
Then on 12 April 1204 the fleet left the northern shore of teh Golden Horn again.
Should the fighting have been much the same as just a few days before, this time there was a vital difference. A wind was blowing from the north. Had the Venetian galleys been driven onto the beach with their bows previously, then now the strong wind drove them further up the beach than the oarsmen alone had managed before. This allowed the Venetians to finally bring their drawbridges up against the heightened towers, which had not been able to do three days earlier.
The knights charged up the drawbridges onto the towers and their drove the men from Varangian Guard back.Two of the wall's defence towers fell early on into the hands of the invaders. In the ensuing chaos crusaders on the shore managed to break through a small gate in the wall and forced their way in. The emperor now made the fatal mistake of not sending forth his Varangian bodyguards who could have driven out the intruders who numbered only about 60. Instead he called up reinforcements to deal with them. It was teh mistake which gave the intruders enough time to open a larger gate through which now mounted knights could enter through the wall.
With the mounted knights now streaming in and charging towards his camp on a hilltop overlooking the scene, Alexius V was forced to retire. He retreated through the streets to the imperial palace of Bouceleon together with his infantry and his Varangian Guard.
The day ended with a substantial part of the northern wall in Venetian hands and grounds beneath it in control of the crusaders. It was at this point that as night set in the fighting came to a halt. But in the minds of the crusaders teh city was far from taken. They expected the fighting still to last for weeks, perhaps even months, as they would be forced to contest control of the city street for street and house by house with embittered Byzantine defenders. In their minds things were far from decided. But the people of Constantinople saw things differently. Their famous walls had been breached. They believed themselves defeated.
People were fleeing the city through the southern gates in droves. The army was utterly demoralized and would hardly fight the intruders. Only the Varangian Guard could be counted on, but they were too few to stem the tide of the crusaders. And the emperor knew that if he was captured, he, the murdered of the crusaders' chosen puppet emperor, could expect only one thing.
Realizing that there was no hope left, Alexius V left the palace and fled the city. Another nobleman, Theodore Lascaris, tried in a desperate bid to motivate the troops and the people for one last time, but it was in vain. He too fled the city that night, heading for Nicaea where he eventually should be crowned emperor in exile.
In the same night, the reasons are unknown, yet another great fire broke out, utterly destroying further parts of ancient Constantinople.

The crusaders awoke the next day, 13 April 1204, expecting the fighting to continue, only to find that they were in control of the city. There was no opposition. The city surrendered.

Thus began the sack of Constantinople, the richest city of all Europe. Nobody controlled the troops. Thousands of defenseless civilians were killed. Women, even nuns, were raped by the crusading army and churches, monasteries and convents were looted. The very altars of churches were smashed and torn to pieces for their gold and marble by warriors who had sworn to fight in service of the Christian faith.
Even the magnificent Santa Sophia was ransacked by the crusaders. Works of tremendous value were destroyed merely for their material value. One such work was the bronze statue of Hercules, created by the famous Lysippus, court sculptor of no lesser than Alexander the Great. The statue was melted down for its bronze. It is but one of a mass of bronze artworks which was melted down by those blinded by greed.
The loss of art treasures the world suffered in the sack of Constantinople is immeasurable.
It is true that the Venetians looted, but their actions were by far more restrained. Doge Dandolo still appeared to have control over his men. Rather than wantonly destroying all around, the Venetians stole religious relics and works of art which they would later take to Venice to adorn their own churches.
In the following weeks a curious election took place in which the conquerors finally decided upon a new emperor. an election it might have been, but it was self-evident that it was the Doge of Venice, Enrico Dandolo, who actually made the decision as to who should rule.
Boniface, the leader of the Crusade would have been the obvious choice. But Boniface was a mighty warrior knight with powerful allies in Europe. The Doge obviously prefered a man to sit on the throne who was less likely to be a threat to the trading powers of Venice. And so the choice fell upon Baldwin, Count of Flanders who had been one of leaders junior to Boniface in the Crusade.

This left the republic of Venice in triumph. Their greatest rival in the Mediterranean was smashed, led by a ruler who would be of no danger to their aspirations of dominating maritime trade. They had successfully diverted the Crusade from attacking Egypt with whom they had signed a lucrative trade agreement. And now many artworks and religious relics would be taken back home to adorned their own great city. Their old, blind Doge, already in his eighties, had served them well.