The Fourth Crusade and the Latin Empire of Constantinople

The Fourth Crusade, originally intended to retake Jerusalem, instead followed a surprising and complex course leading to the capture of Constantinople and the creation of the Latin Empire.

Campaign begins and diversion

In 1202, the Crusader army set sail from Venice with the aim of reaching the Holy Land, but faced immediate difficulties when they could not pay the Venetians for the ships and supplies they had contracted. To settle this debt, the Crusader leaders agreed to Venice's proposal to attack the Christian city of Zara (modern-day Zadar), a rebellious port on the Dalmatian coast. Despite Pope Innocent III forbidding assault on fellow Christians, the city was besieged and captured in November 1202, marking a troubling turn in the Crusade’s course. This early act of violence against a Christian city strained relations with the papacy and foreshadowed the unusual and controversial nature of the expedition.

Move to Constantinople

In early 1203, the Crusaders shifted their focus to Constantinople, the capital of the Byzantine Empire, after receiving a proposal from Alexios IV Angelos, a claimant to the throne. Alexios promised significant financial and military support if the Crusaders helped restore him to power. The army reached Constantinople by June 1203, where they successfully entered the city and installed Alexios IV as emperor. However, his rule was unstable, and political unrest soon erupted. Alexios IV was overthrown and murdered by local factions, leaving the Crusaders in a precarious position.

Siege and sack of Constantinople

Frustrated by broken promises and escalating tensions, the Crusaders launched a full assault on Constantinople in April 1204. The city was fiercely attacked, breached, and brutally sacked over several days. The Crusaders looted countless treasures, destroyed important cultural and religious sites, and caused widespread devastation. This marked one of the most infamous events of the Crusades, as the greatest Christian city was turned against itself by fellow Christians.

Establishment of the Latin Empire

Following the sack, the Crusaders established the Latin Empire of Constantinople on former Byzantine territory. Baldwin of Flanders was crowned as the first Latin Emperor in May 1204, symbolizing the transfer of power from Byzantine to Latin hands. The new empire struggled with ongoing military challenges and political instability but represented a significant and dramatic outcome of the Fourth Crusade’s unexpected course.

The Fourth Crusade ended with the death of its original leader Boniface of Montferrat in 1207, marking the closure of this unusual chapter of medieval history. Throughout the campaign, the Crusade deviated drastically from its original holy mission, culminating instead in a devastating conflict between Christian factions and a new era of Latin rule in Byzantine lands.

The Fourth Crusade led to the shocking sack of Constantinople in 1204, a momentous event that devastated the Byzantine capital. Crusaders looted, destroyed priceless art, and caused deep religious and cultural wounds that intensified the East–West Schism between the Catholic and Orthodox Churches. Instead of recapturing Jerusalem, the crusade established the Latin Empire of Constantinople, a feudal state replacing the Byzantine Empire with a Catholic ruler.

This new empire controlled Constantinople and nearby areas, but much of the former Byzantine territory fragmented into rival states. The Latin Empire faced immediate threats, notably suffering a severe defeat at the Battle of Adrianople (1205) against the Bulgarians, weakening its position. It lasted only around half a century before the Byzantines retook Constantinople in 1261. Meanwhile, Venice retained key colonies in the Aegean and Eastern Mediterranean, influencing regional power long after the empire’s fall. The Fourth Crusade thus accelerated Byzantine decline and indirectly paved the way for later Ottoman conquests.