raid Bosnia in the spring of 1424, just enough to make it clear to Tvrtko that close relations with Venice would not be tolerated. Tvrtko understood that Venice would not be able to provide him with help against the Turks, and thus slowly dismantled their alliance. Although the cooling of Tvrtko's relations with Venice suited Ragusa, another incident guaranteed that the city-state and the King would not be on friendly terms for some more time. In 1424, a kinsman of Tvrtko named Vuk Banić unsuccessfully attempted to usurp the throne with the help of Tvrtko's aunt, Queen Kujava, who wished to avenge her son's deposition. Ragusa had a long-standing tradition of granting political asylum to members of ruling families, and did not fail to accommodate Vuk when he sought sanctuary. The same year, while the Turks were raiding the neighbouring Despotate of Serbia, Tvrtko decided to reclaim Srebrenica, which had been seized by Sigismund in 1411 and granted to his ally, the Serbian ruler Stefan Lazarević. The local Ragusan merchants assisted the Serbs, and the project failed; Stefan's victorious troops went on to plunder Tvrtko's realm when the Turks retreated from their land. Hungarian alliance In 1425, Tvrtko realized that he needed a strong ally in the event of further Turkish attacks. Aware that he could not count on Venice, he decided to improve relations with Hungary, which resulted in a treaty the same or the following year. The Ottomans responded with severe attacks that forced Tvrtko to accept their suzerainty and to agree to paying an annual tribute. The Turks departed in 1426, and he became even more desperate to form an alliance with Hungary. Tvrtko's unfavourable position enabled Sigismund to demand the recognition of the latter's father-in-law, Hermann II of Celje, as heir presumptive to the childless king. Hermann was the son of Tvrtko's aunt Catherine, but was first and foremost a Hungarian count whose kingship was very undesirable to Bosnian nobility. Vuk Banić again presented himself as pretender, and Tvrtko realized that the tide was turning against him. He decided to push the alliance with Hungarian even further, not only recognizing Hermann as his heir presumptive in the fall of 1427, but also negotiating a Hungarian marriage. The chosen bride was Dorothy Garai, daughter of the Ban of Usora. Sandalj and the Zlatonosović family voiced their opposition by shunning the wedding festivities in 1428. Tvrtko eventually reconciled