[2] His latter campaigns in the Balkans were aimed not so much at conquest and subjugation as at drawing the Serbs, Bosnians, Wallachians and Bulgarians into the fold of the Roman Catholic faith and at forming a united front against the Turks, which was also supported by the Pope in Avignon.

Louis first led campaigns against the Bogumils in Bosnia and then he wanted to convert the Orthodox population, which deeply offended the Patriarch in Constantinople.

However, he ended up heading a campaign against the Bulgarian Tsardom of Vidin and its ruler Ivan Sratsimir, which suggests that Vladislav had in the meantime yielded to him.

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.

[citation needed] 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.

The crusaders captured Varna, and from there the prince sent an embassy from the city's inhabitants to Ivan Shishman to free the emperor.

On December 6, 1366, the envoys of Doge Marco Cornaro visited his palace in Vértes and also discussed a possible Hungarian-Venetian anti-Ottoman alliance.

The Bosnian king Tvrtko I recognized Louis as his lord, whom he successfully resisted in 1363, but had to seek protection due to Turkish attacks.

[citation needed] It became clear that Louis no longer had sufficient forces to resolve the Bulgarian and Wallachian issues, which led to the growth of Turkish influence in Wallachia.

The Bulgarians, who won against the Hungarians, were in fact the biggest losers of these wars, as their castles and lands were gradually occupied by the Turks, and by the 15th century the country was already part of the Ottoman empire.