The war arose from the failure of the Truce of Nice, which ended the Italian War of 1536–1538, to resolve the long-standing conflict between Charles and Francis—particularly their conflicting claims to the Duchy of Milan. Having found a suitable pretext, Francis once again declared war against his perpetual enemy in 1542. Fighting began at once throughout the Low Countries; the following year saw the Franco-Ottoman alliance's attack on Nice, as well as a series of maneuvers in northern Italy which culminated in the bloody Battle of Ceresole. Charles and Henry then proceeded to invade France, but the long sieges of Boulogne-sur-Mer and Saint-Dizier prevented a decisive offensive against the French.