While the first three Crusades were launched in an effort to reclaim Jerusalem from Muslims, the Fourth Crusade, begun in 1202, pitted Christians against Christians: Roman Catholics against Orthodox.

Launched by Pope Innocent III to reclaim Jerusalem, the Fourth Crusade instead ended up sacking the Christian city of Constantinople due to debts, Venetian trade‑games and Byzantine intrigue.

This video traces how the Crusader States rose after the astonishing success of the First Crusade—culminating in the capture of Jerusalem—only to collapse by 1291 with the fall of Acre. It explains ...