Siege of Constantinople (1394–1402)

The Crusade of Nicopolis was launched to relieve the city, but it was decisively defeated by the Ottomans. In 1399, a French expeditionary force under Marshal de Boucicaut arrived, but was unable to achieve much. The situation became so dire that in December 1399 the Byzantine emperor, Manuel II Palaiologos, left the city to tour the courts of Western Europe in a desperate attempt to secure military aid. The emperor was welcomed with honours, but secured no definite pledges of support. The city was relieved when Bayezid had to confront the invasion of Timur in 1402. Bayezid's defeat in the Battle of Ankara in 1402 and the subsequent Ottoman civil war enabled the Byzantines to regain some lost territories in the Treaty of Gallipoli.