Why was Bosnia powerful during the reign of King Tvrtko I?

During the reign of Tvrtko I (1353–1391), Bosnia became the most powerful state in the western Balkans due to his successful efforts to consolidate control, recover lost territories, and expand his domain.12

Key factors contributing to this power included:

• Territorial Expansion: After establishing firm control over Bosnia by 1370, Tvrtko recovered lost lands and extended his influence southward into Serbia and along the Adriatic coast, eventually claiming the titles "king of Dalmatia and Croatia" in 1390.312
• Royal Legitimacy: In 1377, he crowned himself "king of the Serbs, of Bosnia, and of the coast," solidifying his status as a major regional sovereign.1
• Military Strength: Tvrtko demonstrated significant military capability, notably by halting an Ottoman Turkish invasion at Bileća in 1388 and contributing a large force to the Battle of Kosovo Polje in 1389.32

This period of "Greater Bosnia" was an exceptional era of independence and dominance for the state, which was otherwise largely landlocked and isolated throughout the medieval period.2