Bayezid I was the Ottoman Sultan from 1389 to 1402. He was the son of Murad I and Gülçiçek Hatun and he built one of the largest armies in the known world at the time and unsuccessfully besieged Constantinople. He was defeated and captured by Timur at the Battle of Ankara in 1402, the first major role of Bayezid was as governor of Kütahya, a city that was conquered from the Germiyanids. He was a soldier, earning the nickname of Lightning in a battle against the Karamanids. Immediately after obtaining the throne, he had his younger brother strangled to avoid a plot, in 1390, Bayezid took as a wife Princess Olivera Despina, the daughter of Prince Lazar of Serbia, who also lost his life in Kosovo. Bayezid recognized Stefan Lazarević, the son of Lazar, as the new Serbian leader, the upper Serbia resisted the Ottomans until general Pashayigit captured the city of Skopje in 1391, converting the city to an important base of operations. Meanwhile, the sultan began unifying Anatolia under his rule, forcible expansion into Muslim territories could endanger the Ottoman relationship with the gazis, who were an important source of warriors for this ruling house on the European frontier. So Bayezid began the practice to first secure fatwas, or legal rulings from Islamic scholars, however he suspected the loyalty of his Muslim Turkoman followers, for Bayezid relied heavily on his Serbian and Byzantine vassal troops to perform these conquests. In a single campaign over the summer and fall of 1390, Bayezid conquered the beyliks of Aydin, Saruhan and his major rival Sulayman, the emir of Karaman, responded by allying himself with the ruler of Sivas, Kadi Burhan al-Din and the remaining Turkish beyliks. At this point, Bayezid accepted peace proposals from Karaman, concerned that further advances would antagonize his Turkoman followers and lead them to ally with Kadi Burhan al-Din. Once peace had been made with Karaman, Bayezid moved north against Kastamonu which had given refuge to many fleeing from his forces, from 1389 to 1395 he conquered Bulgaria and northern Greece. In 1394 Bayezid crossed the River Danube to attack Wallachia, ruled at that time by Mircea the Elder, in 1394, Bayezid laid siege to Constantinople, the capital of the Byzantine Empire. Anadoluhisarı fortress was built between 1393 and 1394 as part of preparations for the Second Ottoman Siege of Constantinople, which place in 1395. On the urgings of the Byzantine emperor Manuel II Palaeologus a new crusade was organized to defeat him and this proved unsuccessful, in 1396 the Christian allies, under the leadership of the King of Hungary and future Holy Roman Emperor Sigismund, were defeated in the Battle of Nicopolis. Bayezid built the magnificent Ulu Cami in Bursa, to celebrate this victory, thus the siege of Constantinople continued, lasting until 1402. The beleaguered Byzantines had their reprieve when Bayezid fought the Timurid Empire in the East, at this time, the empire of Bayezid included Thrace, Macedonia, Bulgaria, and parts of Serbia in Europe. In Asia, his domains extended to the Taurus Mountains and his army was considered one of the best in the Islamic world. In 1397, Bayezid defeated the emir of Karaman in Akçay, killing him, in 1398, the sultan conquered the Djanik emirate and the territory of Burhan al-Din, violating the accord with Timur
Image: Yıldırım I. Bayezit
A manuscript of the Quran from the reign of Bayezid I.