Bayezid I

Bayezid I became sultan in 1389 and moved fast enough to earn the nickname "Thunderbolt." He claimed the title Sultan-i Rûm — sultan of Rome — and set his sights on Constantinople, besieging it without success in 1394. Two years later he shattered a crusader army at Nicopolis in what is now Bulgaria, the kind of victory that makes mapmakers nervous. He spent the next years annexing or vassalizing every beylik in Anatolia, consolidating an empire that had been a patchwork. In 1402 he returned to Constantinople and the siege looked promising this time — until Timur, the Turco-Mongol conqueror, i…