The Ottoman story began not with a vast empire but with a small principality on the turbulent frontier of late-medieval Anatolia. Around the turn of the fourteenth century, Osman I and his followers established themselves in north-western Anatolia, where Byzantine territories, Turkish principalities and shifting networks of warriors and local rulers competed for influence. From these relatively modest beginnings emerged the Ottoman dynasty. Its early rulers gradually expanded their authority, capturing important centres such as Bursa and building a state that drew upon Turkish, Islamic, Byzantine and wider Mediterranean traditions. The conventional date of 1299 is often used for the foundation of the Ottoman state, although its emergence was a gradual process rather than a single moment.

During the fourteenth and fifteenth centuries, Ottoman expansion increasingly turned towards south-eastern Europe. Armies crossed into the Balkans, Ottoman rulers established their power around Adrianople — later Edirne — and Christian princes found themselves alternately fighting, negotiating with or becoming vassals of the expanding dynasty. The Ottoman advance was far from unstoppable. Bayezid I’s defeat by Timur at the Battle of Ankara in 1402 plunged the dynasty into a prolonged succession struggle, but Mehmed I eventually reunited the state. Within a generation, Ottoman power was again advancing on both sides of the Bosporus. This ability to recover from military disaster was one of the defining features of the dynasty’s medieval rise.

The decisive moment came in 1453, when Sultan Mehmed II captured Constantinople after a major siege, bringing the Byzantine Empire to an end and transforming the political landscape of the eastern Mediterranean. Constantinople became the centre of an increasingly ambitious Ottoman imperial state, while Mehmed continued to extend his authority across Anatolia and the Balkans. Yet the medieval Ottoman world was more than a succession of battles and conquests. It was shaped by soldiers and merchants, scholars and administrators, Christians, Muslims and Jews, competing dynasties and intersecting cultures. The articles in this collection explore that formative world: the rulers who built the Ottoman state, the armies that carried it across continents, the societies brought under its authority, and the encounters with Byzantium, the crusading powers and other states that helped reshape the final centuries of the Middle Ages.