Ban of Croatia, Dalmatia and Slavonia
Nicholas was first styled as the ban of Croatia and Dalmatia in a royal diploma issued in December. Historian Stanko Andrić proposes that King Sigismund promoted Nicholas to the new office most probably after the successful royal campaign against Bosnia in July. Before the end of the year, Nicholas routed Vuk Vukčić whom Ladislaus of Naples had appointed to represent him as his ban in the two realms. After his victory, the burghers of Split elected him the count of the town.
Nicholas left Croatia and Dalmatia to join Sigismund 's invasion of Wallachia in July 1395. He and Peter Perényi commanded the rearguard during the withdrawal of the royal troops from Wallachia. He spent several months in his estates before returning to Croatia. He and John Szepesi, Bishop of Zagreb, jointly presided the sabor (or general assembly) in July 1396.
Nicholas accompanied Sigismund to a large-scale military campaign against the Ottoman Empire in 1396. The crusade ended with the Ottomans' great victory in the Battle of Nicopolis on 25 September, but Nicholas was one of the few who could flee from the battlefield. The Sigismund's defeat outraged Stephen II Lackfi, one of the noblemen whom Sigismund had appointed to rule the country during his absence. He and his nephew approached Ladislaus of Naples, who had not abdicated his claim to Hungary.
Nicholas came back from the crusade in King Sigismund's retinue. They landed at Split in Dalmatia on 21 December 1396. Before the end of the year, the burghers of Split elected Nicholas their count. The king and Nicholas put an end to the movements of the supporters of Ladislaus of Naples in the Dalmatian towns before hurrying to Križevci. The two Lackfis were summoned to the town where they were captured and murdered on 27 February 1397. Historian László Markó says, Nicholas and Hermann of Celje enticed them to come to Slavonia to facilitate their murder. Another historian, Elemér Mályusz, emphasizes that the exact circumstances of the purge are unknown, but he proposes that John Kanizsai, Archbishop of Esztergom, was most probably its initiator. After the "Bloody Sabor of Križevci" Sigismund made Nicholas Ban of Slavonia.
King Sigismund granted Osor and Cres in Dalmatia to Nicholas and his brother in May. The two estates had been possessed by John Szerecsen and his sons, who failed to pay the taxes due to the bans. Sigismund held a Diet (or legislative assembly) at Temesvár (now Timișoara in Romania) to adopt measures to secure the defense of the southern frontier of the kingdom. At the Diet, the king granted "the banship of Dalmatia, Croatia and Slavonia together with its appurtenances and income" on 2 November 1397 to Nicholas and John Garai for the rest of their lives.
