[2][9][13] Queen Joanna I of Naples officially acknowledged Clement VII as the lawful pope against Urban VI on 22 November 1378.

[15] In retaliation, Pope Urban VI excommunicated the queen and declared her deprived of her kingdom in favor of Charles of Durazzo and his wife Margaret on 17 June.

He marched on the Kingdom of Naples with a Croatian army, defeated her husband Otto, Duke of Brunswick-Grubenhagen, at San Germano, seized the city and besieged Joanna in the Castel dell'Ovo.

Louis's expedition counted to some 40,000 troops, including those of Amadeus VI of Savoy, and had the financial support of Antipope Clement VII and Bernabò Visconti of Milan.

Charles, who counted on the mercenary companies under John Hawkwood and Bartolomeo d'Alviano, for a total of some 14,000 men, was able to divert the French from Naples to other regions of the kingdom and to harass them with guerrilla tactics.

The latter was able to conquer Arezzo and then invade the Kingdom of Naples, but midway was reached by the news that Louis had suddenly died at Bisceglie on 20 September 1384.

After six months of siege, Urban was freed by two Neapolitan barons who had sided with Louis of Anjou, Raimondello Orsini and Tommaso di Sanseverino.

It was not difficult for him to take power, as he gained the support of several Croatian lords and many contacts he made during his tenure as Duke of Croatia and Dalmatia.

However, Elizabeth of Bosnia, widow of Louis and mother of Mary, arranged to have Charles assassinated on 7 February 1386.