During the first years of his reign, Louis launched a crusade against the Lithuanians and restored royal power in Croatia; his troops defeated a Tatar army, expanding his authority towards the Black Sea.

His troops occupied large territories on both occasions, and Louis adopted the styles of Neapolitan sovereigns (including the title of King of Sicily and Jerusalem), but the Holy See never recognized his claim.

He waged wars against the Lithuanians, Serbia, and the Golden Horde in the 1350s, restoring the authority of Hungarian monarchs over territories along frontiers that had been lost during previous decades.

[16] Two leading Polish noblemen – Zbigniew, chancellor of Kraków, and Spycimir Leliwita – persuaded Casimir, who had not fathered a son, to make his sister, Elizabeth, and her offspring his heirs.

[19] Historian Paul W. Knoll writes that Casimir preferred his sister's family to his own daughters or a member of a cadet branch of the Piast dynasty, because he wanted to ensure the king of Hungary's support against the Teutonic Knights.

[42] According to the nearly contemporaneous chronicle of John of Küküllő, Louis launched his first campaign against a group of Transylvanian Saxons, who had refused to pay taxes, and forced them to yield in the summer of 1344.

[44] He dispatched Andrew Lackfi, Count of the Székelys, to invade the lands of the Golden Horde in retaliation for the Tatars' earlier plundering raids against Transylvania and the Szepesség (now Spiš in Slovakia).

[58] Louis and his mother accused Queen Joanna I, Prince Robert of Taranto, Duke Charles of Durazzo, and other members of the Neapolitan branches of the Capetian House of Anjou of plotting against Andrew.

[59] Louis also laid claim to the regency of the kingdom during the minority of his nephew, referring to his patrilinear descent from the first-born son of Robert the Wise's father, Charles II of Naples.

[75] After their arrival, King Louis's "smile was replaced by the harshest expression as he unveiled with terrible words the true feelings he had for the princes and that he had kept hidden until then", according to the contemporaneous Domenico da Gravina.

[91] Although the Black Death was less devastating in the sparsely populated Hungary than in other parts of Europe, there were regions that became depopulated in 1349, and the demand for work force increased in the subsequent years.

[101] According to the contemporaneous historian Matteo Villani, Louis attempted to "leave the kingdom without losing face" after he had run out of money and experienced the resistance of the local population.

[103][104][105] The pope promised Louis that the queen's role in her husband's murder would again be investigated, and he ordered her to pay 300,000 gold florins as a ransom for the imprisoned Neapolitan princes.

[105] Casimir III of Poland urged Louis to intervene in his war with the Lithuanians who had occupied Brest, Volodymyr-Volynskyi, and other important towns in Halych and Lodomeria in the previous years.

[104] A papal legate visited Louis to persuade him to wage war against Stefan Dušan, Emperor of the Serbs, who had forced his Roman Catholic subjects to be re-baptised and join the Serbian Orthodox Church.

[clarification needed][114][115] At the same Diet, Louis ordered that all landowners were to collect the "ninth", that is one tenth of specified agricultural products, from the peasants who held plots on their estates.

[118] Louis even renounced the ransom that Joanna I had promised to pay for the liberation of the imprisoned Neapolitan princes, stating that he had not gone to "war for greed, but to avenge the death of his brother".

[129] The young Tatar ruler, whom historian Iván Bertényi identified as Jani Beg, did not want to wage war against Hungary and agreed to sign a peace treaty.

[134] Upon his order, Croatian lords besieged and captured Klis, a Dalmatian fortress that Stefan Dušan's sister, Jelena, had inherited from her husband, Mladen Šubić.

[140] The pope made Louis the "standard-bearer of the Church" and granted him a three-year tithe to fight against Francesco II Ordelaffi and other rebellious lords in the Papal States.

[144] The Dalmatian towns remained self-governing communities, owing only a yearly tribute and naval service to Louis, who also abolished all commercial restrictions that had been introduced during the Venetians' rule.

Fine and Pál Engel write that the Serbian lord was a member of the Rastislalić family;[147][148] Gyula Kristó and Iván Bertényi identify him as Lazar Hrebeljanović.

[173] However, Louis made every effort to hinder the activities of the papal tax collectors, stating that he needed resources to cover the costs of his future wars against the infidels and the pope's enemies in Italy.

[175] In September, Louis visited Kraków to attend the large congress where Peter I of Cyprus attempted to persuade a dozen European monarchs to join the crusade.

[163][206] After his meeting with Louis in 1372, the papal legate, John de Cardailhac, stated: "I call God as my witness that I have never seen a monarch more majestic and more powerful ... or one who desires peace and calm as much as he.

[233][236] Taking advantage of the situation, Władysław the White, Duke of Gniewkowo, who was a male member of the royal Piast dynasty, announced his claim to the Polish crown.

[262] According to the Chronicle of Parthénope, the Neapolitan princes whom Louis had imprisoned during his first campaign in Southern Italy proposed him to marry Queen Joanna I's younger sister and heir, Mary.

[1] Historian Enikő Csukovits writes that Louis's military actions show that he continued and accomplished his father's policy through recovering Croatia and Dalmatia and waging wars in Southern Italy, in Lithuania and in the Balkan Peninsula.

[61][207] For instance, in 1845 the poet Sándor Petőfi referred to Louis's reign as a period when "the falling stars of the north, the east and the south were all extinguished in Hungarian seas".

[279] New palaces and castles built at Zólyom, Diósgyőr and Louis's other favorite hunting places were "masterpieces of the highest European standards" of his age, according to historian László Kontler.