A fleet of Burgundian crusaders attacked the Ottoman fleet on the Black Sea in the spring 1445. The commander of the fleet, Walerand of Wavrin, sent envoys to Hungary to start negotiations about a joint campaign against the Ottoman Empire. At Hunyadi's request, one of Wavrin's envoys, Pedro Vasque de Saavedra, visited Vlad and convinced him to meet Wavrin. In July, Vlad went to Isaccea where he made an alliance with Wavrin. Vlad mustered an army of 4,000–6,000 strong and placed it under the command of his son, Mircea.