The Italian War of 1521-26 (Four Years' War, part of the Italian Wars) pitted Francis I of France and the Republic of Venice against the Holy Roman Emperor Charles V, Henry VIII of England, and the Papal States. The conflict arose from animosity over the election of Charles as Emperor in 1519-20 and from Pope Leo X's need to ally with Charles against Martin Luther. The Battle of Pavia, fought on the morning of February 24, 1525, was the decisive engagement of the Italian War of 1521-26. An Imperial-Spanish army under the nominal command of Charles de Lannoy (and working in conjunction with the garrison of Pavia, commanded by Antonio de Leyva) attacked the French army under the personal command of Francis I of France in the great hunting preserve of Mirabello outside the city walls. In the four-hour battle, the French army was split and defeated in detail. The French suffered massive casualties, including many of the chief nobles of France. Francis himself was captured by Habsburg troops and imprisoned by Charles V and forced to sign the humiliating Treaty of Madrid, surrendering significant territory to his captor. The outcome of the battle cemented Habsburg ascendancy in Italy.