>> Rise of the Ottoman Empire (1299–1453)

Ertuğrul, the father of Osman I (founder of the Ottoman Empire), arrived in Anatolia from Merv (Turkmenistan) with 400 horsemen to aid the Seljuks of Rum against the Byzantines. After the demise of the Turkish Seljuk Sultanate of Rum in the 14th century, Anatolia was divided into a patchwork of independent, mostly Turkish states, the so-called Ghazi emirates. One of the emirates was led by Osman I (1258–1326), from whom the name Ottoman is derived. Osman I extended the frontiers of Turkish settlement toward the edge of the Byzantine Empire. It is not well understood how the early Ottomans came to dominate their neighbours, as the history of medieval Anatolia is still little known.

In the century after the death of Osman I, Ottoman rule began to extend over the Eastern Mediterranean and the Balkans. Osman's son, Orhan, captured the northwestern Anatolian city of Bursa in 1324, and made it the new capital of the Ottoman state. This Ottoman conquest meant the loss of Byzantine control over northwestern Anatolia. The important city of Thessaloniki was captured from the Venetians in 1387. The Ottoman victory at Kosovo in 1389 effectively marked the end of Serbian power in the region, paving the way for Ottoman expansion into Europe. The Battle of Nicopolis in 1396, widely regarded as the last large-scale crusade of the Middle Ages, failed to stop the advance of the victorious Ottoman Turks.

Battle of Nicopolis in 1396. Painting from 1523.

With the extension of Turkish dominion into the Balkans, the strategic conquest of Constantinople became a crucial objective. The empire had managed to control nearly all former Byzantine lands surrounding the city, but in 1402 the Byzantines were temporarily relieved when the Turco-Mongol leader Timur, founder of the Timurid Empire, invaded Anatolia from the east. In the Battle of Ankara in 1402, Timur defeated the Ottoman forces and took Sultan Bayezid I as a prisoner, throwing the empire into disorder. The ensuing civil war lasted from 1402 to 1413 as Bayezid's sons fought over succession. It ended when Mehmed I emerged as the sultan and restored Ottoman power, bringing an end to the Interregnum, also known as the Fetret Devri.

Part of the Ottoman territories in the Balkans (such as Thessaloniki, Macedonia and Kosovo) were temporarily lost after 1402 but were later recovered by Murad II between the 1430s and 1450s. On 10 November 1444, Murad II defeated the Hungarian, Polish, and Wallachian armies under Władysław III of Poland (also King of Hungary) and John Hunyadi at the Battle of Varna, the final battle of the Crusade of Varna, although Albanians under Skanderbeg continued to resist. Four years later, John Hunyadi prepared another army (of Hungarian and Wallachian forces) to attack the Turks but was again defeated by Murad II at the Second Battle of Kosovo in 1448.
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