The Fourth Crusade, unable to pay Venice for its transport, was diverted first to Zara and then to Constantinople, where after intervening in a Byzantine succession dispute it stormed the city on 12–13 April 1204 and sacked it for three days. Niketas Choniates, an eyewitness, records systematic plunder, killings, rape and the desecration of churches including Hagia Sophia; Villehardouin, on the crusader side, records the scale of the booty without demur. Britannica's summary gives approximate campaign losses of about 20,000 on the crusader side and 30,000 on the Byzantine, with civilian deaths unknown; no contemporary source provides a civilian toll. The empire was partitioned among the victors, its relics and treasures dispersed to Latin churches, and although Byzantine rule was restored at Constantinople in 1261 the state never recovered its former reach. Pope John Paul II expressed regret for the sack in 2001; that is a statement of contrition, not a formal legal finding.
A Venetian-transported crusade army diverted to Constantinople, stormed and sacked the city in April 1204, and partitioned the Byzantine empire among Latin rulers
Reconstructed from the walled area, grain supply and pilgrim descriptions rather than any register. Magdalino and others put the twelfth-century city at roughly 400,000, the largest in Christendom; more conservative estimates run to 150,000-250,000, and the city never recovered its size after 1204.
No defensible figures for civilian deaths. Contemporary accounts describe killing during three days of sack without totals; the figures of roughly 20,000 crusader and 30,000 Byzantine losses that appear in reference summaries refer to the campaign and are not derived from a count of the sack itself.
Niketas Choniates, an eyewitness, documents rape, the plundering and burning of houses and the desecration and stripping of churches including Hagia Sophia; Villehardouin corroborates the scale of the plunder.
Bulgaria, Turkey, Greece