Bayezid I:  

Bayezid (1360-1403)  bey/sultan from 1389 till 1403. His byname was Yildirim, "Thunderbolt". Bayezid represents both a continuation of the building of state structures in the empire, as well as the most dramatic downturn to date in its history.
 
He consolidated the process of centralization of the state begun under Murat I. But his main achievements came in Asia. For while he undertook many important military campaigns in Europe, he put most of his emphasis on widening Ottoman suzerainty over Turkman rulers in Anatolia itself. Various emirates were annexed into the empire. But this  policy also brought him into direct conflict with Timur Lenk ("Timerlane"). And this resulted, in 1402, in a total defeat for Beyazid.

BIOGRAPHY
Around 1360: Born as son of of sultan Murad 1.
1391: A 8-year long blockade against Constantinople is started.
1393 July: Tirnova in today's Bulgaria is blockaded by Bayezid's forces.
1394 April: Salonika in today's Greece is conquered.
1396 September 25: Bayezid is faced with a Hungarian-Venetian crusade;  at Nicopolis he inflicts a crushing defeat.
1402 July: In the battle of Ankara against Timur Lenk, Bayezid's forces are defeated and Bayezid taken prisoner
1403: Dies in Aksehir while in capitivity. He was eventually succeeded by his son Mehmed 1, but only after a lengthy interregnum during which time he was forced to win back the lands that had been given to his 2 brothers Süleyman and Isa.