The main roads through Albania and the most common Ottoman invasion routes
Skanderbeg, the ruler of Albania (Latin: dominus Albaniae), had served for several years in the Ottoman army, as both soldier and commander, before returning to his homeland and beginning an uprising against the Ottoman Empire in 1444. The Second Battle of Kosovo in 1448 had ended with the defeat of John Hunyadi, voivode of Transylvania while Skanderbeg and his forces were on their way; but did not arrive due to his army being blocked off by Đurađ Branković, and so he was unable to provide help; Hunyadi engaged the Ottomans thinking Skanderbeg was not coming. In reparation, Skanderbeg ravaged Brankovic's domains. As a result of the defeat, the Ottomans were free from Hungarian pressure, which had been limited to Belgrade and its environs. In 1455, Skanderbeg laid siege to Berat, a fortress which had been seized from his control in 1450. The result was catastrophic for the Albanians who succumbed to an Ottoman counterattack upon Skanderbeg's temporary departure from the main force. Alfonso V of Aragon, Skanderbeg's most helpful and important ally, also suffered a blow to his ambitions which included a pan-Mediterranean empire. The Albanians, however, were able to recover their morale when Pope Calixtus III, who had begun to worry that his plans for crusade would be undermined, promised to aid Skanderbeg.
Before the planned crusade commenced, Sultan Mehmed II the Conqueror (Turkish: el-Fātiḥ) decided to march against Hungary and Albania. In April 1456, Skanderbeg sent Pal Engjëlli, his ambassador to the West, with a letter to Cardinal Domenico Capranica informing the Holy See of his need for aid. The Ottoman invasion came in May 1456 when Moses Golemi, Skanderbeg's former captain who had deserted after loss of Berat, met Skanderbeg's men at the Battle of Oranik. The force was defeated and, through a show of mercy, Golemi was allowed to return to the Albanian ranks without punishment. In July 1456 Mehmed marched a large army to besiege Hungarian-held Belgrade in Serbia, but was defeated by Hunyadi. Later that year, İbrahim II of the Karamanid Dynasty tried to create an anti-Ottoman alliance which would include his realm, Skanderbeg, Hunyadi, Calixtus, and Alfonso, all of whom would act in concert to defeat the sultan. The plans were never put to practice, however.
Skanderbeg's resources were worn out after over a decade of continuous war. Alfonso and the pope could not provide for him fully, while Venice continued to undermine Skanderbeg. The latter considered war with Skanderbeg since he maintained his alliance with Aragon. Relations with the Italian state worsened further when Lekë Dukagjini, Skanderbeg's elusive ally in the north, captured Dagnum. Even though Skanderbeg did not participate in this, Venice used it as a casus belli to launch an expedition against Skanderbeg. War never started but Albanian-Venetian relations sunk to their lowest point. The Venetian rectors continued to provoke Skanderbeg at a time when he had grown relatively weak due to his nephew and one of his most important officers, Hamza Kastrioti, deserting and joining the Ottomans. Hamza had become dissatisfied with Skanderbeg's growing power and, upon being received by the sultan, was offered control over much of Albania once conquered. Stung by the betrayal, Skanderbeg offered an ultimatum to Venice where they had to halt their provocations or begin war. Since a crusade was anticipated against the Ottomans, Venice did not want to seem pro-Ottoman and eased their stance towards Albania.