Stephen Thomas ( Serbo-Croatian : Stefan Tomaš / Stefan Tomaš , Stjepan Tomaš / Stjepan Tomaš ; c. 1411 – July 1461), a member of the House of Kotromanić , reigned from 1443 until his death as the penultimate king of Bosnia . An illegitimate son of King Ostoja, Thomas succeeded King Tvrtko II, but his accession was not recognized by the leading magnate of the Kingdom of Bosnia, Stjepan Vukčić Kosača. The two engaged in a civil war which ended when the King repudiated his wife, Vojača, and married the insubordinate nobleman's daughter, Catherine. Thomas and his second wife, both raised in the Bosnian Church tradition, converted to Roman Catholicism and sponsored construction of churches and monasteries throughout the kingdom. Throughout his reign, Thomas waged a war with the Serbian Despotate over the lucrative mining town of Srebrenica and its surroundings, in addition to (or in conjunction with) multiple conflicts with his father-in-law. Moreover, he had a tense relationship with the menacing Ottoman Empire. After years of skirmishes and raids, Thomas appeared willing to lead the Christian coalition against the Turks, but received no assistance from fellow Christian rulers. Having failed to expand into Croatia proper, Thomas turned again to the east in 1458, arranging a match between his son Stephen and the Serbian heiress Helena. Bosnian control over the remnants of the Serbian Despotate lasted merely a month before the Ottoman conquest of the state. King Thomas' failure to defend Serbia permanently damaged his reputation in Europe. Wishing to improve his image among Europe's Catholics, Thomas turned against the Bosnian Church, thus becoming the first ruler of Bosnia to engage in religious persecution. Thomas' sometime contradictory traits earned him both admiration and scorn from his contemporaries. His son Stephen succeeded him, and immediately proved more apt at dealing with the challenges of the time.
