The Latin Empire was the crusader state established at Constantinople in 1204, which spent fifty-seven years insolvent, shrinking and selling its relics, and fell to eight hundred men in 1261.
The Latin Empire was created in 1204 by a crusade that had set out for Egypt, been diverted to Constantinople by Venetian debt and a Byzantine succession dispute, and taken and sacked the largest Christian city in the world.
The victors partitioned the empire on paper — a quarter and a half of a quarter to the emperor, the rest to Venice and the crusader lords — and then discovered that holding it was a different problem from dividing it.
For fifty-seven years the Latin Empire held Constantinople, a shrinking strip of Thrace, and the loyalty of vassal states in Greece that mostly ignored it. It never solved its finances, never held its frontiers, and ended without a fight.
The sack of April 1204 was catastrophic and the loot was legendary — the bronze horses that stand in Venice were taken from the hippodrome then. It also destroyed the city's economy and much of its population, which the new rulers then had to govern.
Baldwin of Flanders was elected emperor and crowned in Hagia Sophia. Venice took the harbours and the islands, which was the arrangement Venice had wanted all along and the only part of the settlement that made money.
Within a year Baldwin was captured by the Bulgarian tsar Kaloyan at Adrianople and died in captivity, and the empire never recovered the initiative. His brother Henry, who ruled to 1216, was the one competent emperor it had.
The Latin Empire is the clearest case in this archive of a state that could not pay for itself. Its territory shrank almost continuously, its revenues collapsed with the city's trade, and its emperors spent their reigns touring western Europe asking for money.
Baldwin II, the last emperor, sold the relics. The Crown of Thorns went to Louis IX of France in 1238, who built the Sainte-Chapelle in Paris to house it, and a stream of other relics followed it west.
When the relics ran out he pawned his own son to Venetian merchants as security for a loan, and had the lead stripped from the roofs of the imperial palaces to sell. The city he ruled had lost most of its population and much of it stood empty.
Baldwin I (1204–1205), count of Flanders, was elected emperor and captured by the Bulgarians at Adrianople within a year.
Henry of Flanders (1206–1216), his brother, was by common consent the ablest of them: a capable soldier and a conciliator who treated his Greek subjects as subjects rather than enemies, and whose death removed the empire's only chance of stability.
Peter of Courtenay and Robert followed without distinction, and Baldwin II (1228–1261) reigned for thirty-three years, most of them abroad raising money, and fled the city by sea in July 1261.
By 1261 the empire was Constantinople and very little else, and its defence rested on the Venetian fleet. In July that fleet sailed to attack an island in the Black Sea.
A Byzantine reconnaissance force of about eight hundred men, which had no orders to attack, found the city undefended and walked in through a postern gate on the night of 25 July. Baldwin II abandoned his crown and sword and took ship.
The Latin Empire ended there. Its titular claim was inherited and traded among western noble families for another century and a half, which is the only afterlife it had.
The damage was permanent. The sack of 1204 and the fifty-seven years that followed destroyed Constantinople as an economic centre, and the restored empire inherited a capital that was a fraction of what it had been.
The schism between the Greek and Latin churches, formally dated to 1054, became real in 1204 and has effectively never healed. No amount of negotiated union afterwards — including Michael VIII's at Lyons in 1274 — could get past what had been done to the city.
And the strategic consequence outlived everyone involved. A weakened Byzantium could not hold Anatolia, and the Turkish emirates that filled that space produced the Ottomans. The crusade that was meant to help the eastern Christians is the largest single reason they were conquered.