In 1457, Skanderbeg had achieved his most famous victory over the Ottoman Empire at Albulena (Ujëbardha), which was received with great enthusiasm throughout Italy. In order to repay Alfonso for the financial and military assistance given to him years before, Skanderbeg took up the pope's pleas to help out Alfonso's son by sending a military expedition to Italy. Before leaving, Skanderbeg tried to negotiate a ceasefire with Sultan Mehmed II, the conqueror of Constantinople, to ensure his domain's safety. Mehmed had not declared a truce and he was still sending his armies against Bosnia and the Byzantine Morea. It was not until 1459, after Mehmed's conquest of Serbia, that Mehmed not only declared a truce, but also a three-year ceasefire with Skanderbeg. This gave Skanderbeg his opportunity to send his men to Italy.