 The Ottoman wars instigated great demographic changes.During the 16th century Croats from western and northern Bosnia, Lika, Krbava, the area between the rivers of Una and Kupa and especially from western Slavonia migrated towards Austria and the present-day Burgenland Croats are direct descendants of these settlers.To replace the fleeing population, the Habsburgs encouraged the populations of Bosnia to provide military service in the Military Frontier.