By the end of September, Charles was in Majorca, preparing an attack on Algiers; Francis, considering it impolitic to attack a fellow Christian who was fighting the Muslims, promised not to declare war for as long as the Emperor was campaigning. The Imperial expedition, however, was entirely unsuccessful; storms scattered the invasion fleet soon after the initial landing, and Charles had returned to Spain with the remainder of his troops by November. On 8 March 1542, the new French ambassador, Antoine Escalin des Eymars, returned from Constantinople with promises of Ottoman aid in a war against Charles. Francis declared war on 12 July, naming various injuries as the causes; among them was Rincon's murder, which he proclaimed "an injury so great, so detestable and so strange to those who bear the title and quality of prince that it cannot be in any way forgiven, suffered or endured".