Alexios Palaiologos is instrumental in the suppression of the attempted coup by John Komnenos the Fat in July 1201.

After the rebels had seized control of most of the Great Palace, Alexios is sent by the emperor with troops and boats from the Blachernae to the eastern shore of the city.

Here they meet up with the Great Palace's guard, and clear the palace and the Hippodrome of the supporters of the usurper, who is caught and beheaded.

Alexios Mourtzouphlos is likely put in prison for his role in this affair (he is known to have been in prison in 1203), and the two Komnenos brothers, Alexios and David, seem to have fled the capital immediately after the coup's failure.

Alexios is injured in February 1201 or 1202 when the imperial tent collapses during an earthquake, but in the same summer he leads the campaign that subdues the rebellion of governor John Spyridonakes in eastern Macedonia, forcing the latter to flee to Bulgaria.

Pope Innocent III, a primary organizer of the Venetian-backed Fourth Crusade—composed largely of Frenchmen, Venetians, and other Italians, collectively called Franks or Latins—has been unable to prevent its diversion, by the Venetians, to capture Constantinople.

Constantinople’s new coemperors, Isaac II Angelos and his son Alexios IV are unable to pay their debts to the West or to unite the two churches.

They have inspired little confidence among the people of Constantinople in their efforts to defend the city from the Latins and Venetians, who are restless and riot when the money and aid promised by Alexios IV is not forthcoming.

The courtier Alexios Doukas Mourtzouphlos, related to the imperial Doukas family, emerges as a leader of the anti-Latin movement and personally leads some skirmishes against the crusaders.

Heavy taxation, as well as wanton behavior on the part of the crusaders in Constantinople, causes a national revolt at the end of January 1204, when the populace of Constantinople rebels and tries to proclaim a rival emperor in Hagia Sophia.

The emperors barricade themselves in the palace and entrust Doukas with a mission to seek help from the crusaders.

Instead, Doukas uses his access to the palace to arrest the emperors, imprisoning both Alexios IV and his father on the night of January 27-28, 1204.

Alexios V Doukas, crowned in early February 1204, has Alexios IV strangled on February 8.

Isaac II dies soon afterwards, his death variously attributed to fright, sorrow, or foul play.

Alexios makes parts of the Crimea tributary to Trebizond.

Cherson, …

…Kerch, and their hinterlands are governed as an overseas province called Perateia ('beyond the sea').

Alexios V had begun after his coronation to strengthen the defenses of Constantinople and ended negotiations with the Latins, disavowing Alexios IV's debt to the crusaders.

It is too late, however, for the new Emperor to make much of a difference.

An attempted surprise attack against the crusader camp fails despite the emperor's personal leadership.

During the ensuing fight, he defends the city with courage and tenacity, beating back the crusader assault of April 9.

On April 12, 1204, a strong northern wind aids the Venetian ships to come close to the wall.

After a short battle, approximately seventy crusaders manage to enter the city.

Some Crusaders are eventually able to knock holes in the walls, small enough for a few knights at a time to crawl through; the Venetians are also successful at scaling the walls from the sea, though there is extremely bloody fighting with the Varangians, at this time composed of English and Danes.

The crusaders capture the Blachernae section of the city in the northwest and use it as a base to attack the rest of the city, but while attempting to defend themselves with a wall of fire, they end up burning down even more of the city, leaving fifteen thousand people homeless.

The crusaders' second attack proves too strong to repel, and Alexios V flees into Thrace on the night of April 12, 1204, accompanied by Eudokia Angelina and her mother Euphrosyne Doukaina Kamatera.

Constantinople is under Latin control by the next day, the great city having for the first time in its long history; it is subjected by the foot soldiers to pillage and massacre for three days.

During the horrible and savage sacking inflicted on Constantinople by the crusaders, many ancient and medieval Roman and Greek works are either stolen or destroyed.

The magnificent Library of Constantinople is destroyed.

Despite their oaths and the threat of excommunication, the Crusaders ruthlessly and systematically violate the city's holy sanctuaries, destroying, defiling, or stealing all they can lay hands on; nothing is spared.

It is said that the total amount looted from Constantinople was about nine hundred thousand silver marks.

The Venetians receive one hundred and fifty thousand silver marks that is their due, while the Crusaders receive fifty thousand silver marks.

A further one hundred thousand silver marks are divided evenly up between the Crusaders and Venetians.

The remaining half-million silver marks are secretly kept back by many Crusader knights.

Many priceless icons, relics, and other objects will later turn up in western Europe, a large number in Venice.

The huge tenth-century altarpiece later known as the Pala d'Oro, as well as magnificent reliquaries, book covers, and four bronze horses (later to grace the entrance of Saint Mark's Basilica), are among the rich booty taken to Venice from Constantinople.

The Venetians and crusaders themselves take over the city and the government of the empire.

It is decided that twelve electors—six Venetians and six crusaders—should choose an emperor who will have one-quarter of the imperial domain.

The other three-quarters are to be divided.

The clergy of the party not belonging to the emperor elect are to have Hagia Sophia and choose a patriarch.

A small amount of property is specifically designated to support the clergy.

The rest is to be considered booty and divided.

Constantine Laskaris, one of the city's leading defenders, had meanwhile been proclaimed emperor in the Cathedral of St. Sophia as Constantine XI; he and other refugees now flee to Bursa.

Shortly before the fall of Constantinople to the Fourth Crusade, the twenty-two year old Alexios Komnenos, the eldest son of Manuel Komnenos and of Rusudan, daughter of George III of Georgia (and thus a grandson of the dethroned Emperor Andronikos I) had occupied Trebizond in April 1204 with the aid of a Georgian contingent provided by his aunt, Queen Tamar of Georgia.

The Komnenos family is popular on the Black Sea coast, from which it had come originally and had long ties to the region.

In 1182 his grandfather Andronikos had had a stronghold at Oinaion between …

…Sinope and …

…Trebizond.

These three places all declare for Alexios, and while he remains cautiously in the neighborhood of Trebizond, …

…his brother David, aided by the Georgians and local mercenaries, makes himself master of Pontus and Paphlagonia, including Kastamonou, said to be the ancestral castle of the Komnenoi.

David continues on as the "herald and forerunner" of his brother seizing the cities of Kerasus, Limnia, Samsun, Kotyora, and Amastris.

Without a doubt, his march is aided by his family's popularity in the region and by the news of the fall of Constantinople to the Latins.