Orkhan’s son Süleyman died unexpectedly in 1357 and his second son Murad became his heir. Murad launched an offensive against Edirne in 1359 and the city surrendered in 1361. He succeeded Orkhan in 1362 (he ruled until 1389 as Murad I), and made Edirne, on the European mainland, his capital in 1369. In 1371 the rulers of the Balkans acknowledged Ottoman suzerainty, as did the Byzantine emperor c.1372, thus becoming a vassal of the Ottomans; his son, Andronicus IV, only succeeded to the Byzantine throne in 1376 because of Ottoman protection.

In western Anatolia, Ankara was captured in 1354 marking the start of Ottoman east-ward expansion into former Saljuq-Mongol lands. Thus by 1380 the Ottomans were lords of an embryo-empire in Anatolia and the Balkans, which was being expanded and consolidated during successive reigns. The only resistance came from the Karamanlis, the most powerful of the Turcoman frontier-beys in the south, who had established themselves in the old Saljuq capital of Konya and considered themselves the heirs to the Saljuqs; however, in 1387 Murad marched on Konya and won a pitched battle there, thus crushing resistance to his supremacy in Anatolia. He was mortally wounded on the battle-field in 1389 having returned to the Balkans to deal victoriously with a revolt there by the Serbs, Bosnians and Bulgarians. This pattern of dealing with a problem in the East only to be met with a new problem in the West was a recurrent theme during the entire history of the Ottoman empire.