European monarchs to join the crusade. Louis was the only monarch to promise assistance, but later failed to fulfill his promise. At the congress, Casimir III of Poland confirmed Louis's right to succeed him in Poland if he died without a male issue. Louis, who had not fathered a son either, invited a distant relative of his, Charles of Durazzo, to Hungary in 1364, but did not make the young prince his official heir. Louis allowed the Jews to return to Hungary in the same year; legal proceedings between the Jews and those who had seized their houses lasted for years. Louis assembled his armies in Temesvár (now Timișoara in Romania) in February 1365. According to a royal charter that year, he was planning to invade Wallachia because the new voivode, Vladislav Vlaicu, had refused to obey him. However, he ended up heading a campaign against the Bulgarian Tsardom of Vidin and its ruler Ivan Sratsimir, which suggests that Vladislav Vlaicu had in the meantime yielded to him. Louis seized Vidin and imprisoned Ivan Stratsimir in May or June. Within three months, his troops occupied Ivan Stratsimir's realm, which was organized into a separate border province, or banate, under the command of Hungarian lords. The Byzantine Emperor, John V Palaiologos visited Louis in Buda in early 1366, seeking his assistance against the Ottoman Turks, who had set foot in Europe. This was the first occasion that a Byzantine Emperor left his empire to plead for a foreign monarch's assistance. According to Louis's physician, Giovanni Conversini, at his first meeting with Louis, the emperor refused to dismount and to take off his hat, which offended Louis. John V pledged that he would promote the union of the Byzantine Church with the Papacy, and Louis promised to send him help, but neither the emperor nor Louis fulfilled their promises. Pope Urban encouraged Louis not to send help to Constantinople before the emperor guaranteed the Church union. Louis stayed in Transylvania between June and September 1366, implying that he waged war against Moldavia. He issued a decree authorizing the Transylvanian noblemen to pass judgments against "malefactors belonging to any nation, especially Romanians". He also decreed that testimony of a Romanian knez who had received a royal charter of grant weighed the same as that of a nobleman. In the same year, Louis granted the Banate of Severin and the district of Fogaras to