Warfare in the Italian Wars was a complicated and ever-changing art. Much of the period saw revolutionary developments in formation, equipment, and tactics as the great powers of Europe attempted to gain a decisive advantage against each other.
The war arose from the failure of the Truce of Nice, which ended of the Italian War of 1536–38, to resolve the long-standing conflict between Charles and Francis. 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 a joint Franco-Ottoman 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 and Saint-Dizier prevented a decisive offensive against the French.
Charles came to terms with Francis by the Treaty of Crépy in late 1544, but the death of Francis's younger son, the Duke of Orléans—whose proposed marriage to a relative of the Emperor was the cornerstone of the treaty—made it moot less than a year afterwards. Henry, left alone but unwilling to return Boulogne to the French, continued to fight until 1546, when the Treaty of Ardres finally restored peace between France and England. The deaths of Francis and Henry in early 1547 left the resolution of the Italian Wars to their heirs.
Guillaume Gouffier, Seigneur de Bonnivet (c. 1488–February 24, 1525) was a French soldier. In the imperial election of 1519 he superintended the candidature of Francis, and spent vast sums of money in his efforts to secure votes, but without success. An implacable enemy of the Constable de Bourbon, he contributed to the downfall of the latter. In command of the army of Navarre in 1521, he occupied Fuenterrabia and was probably responsible for the renewal of hostilities resulting from its not being restored. Bonnivet succeeded Odet de Foix, Vicomte de Lautrec, in 1523, as commander of the army of Italy and entered the Milanese, but was defeated and forced to effect a disastrous retreat, in which the chevalier Bayard perished. He was afterwards one of the principal commanders of the army which Francis led into Italy at the end of 1524, and died at the Battle of Pavia.