Answer based on context:

On the Continental front, Henry II allied with German Protestant princes at the Treaty of Chambord in 1552. An early offensive into Lorraine was successful, with Henry capturing the three episcopal cities of Metz, Toul, and Verdun, and securing them by defeating the invading Habsburg army at the Battle of Renty in 1554. However, the French invasion of Tuscany in 1553, in support of Siena attacked by an imperial‐Tuscany army, was defeated at the Battle of Marciano by Gian Giacomo Medici in 1554. Siena fell in 1555 and eventually became part of the Grand Duchy of Tuscany founded by Cosimo I de' Medici. The Treaty of Vaucelles was signed on 5 February 1556 between Philip II of Spain and Henry II of France. Based on the terms of the treaty, the territory of the Franche-Comté was relinquished to Philip. However, the treaty was broken shortly afterwards. After Charles' abdication in 1556 split the Habsburg empire between Philip II of Spain and Ferdinand I, the focus of the war shifted to Flanders, where Philip, in conjunction with Emmanuel Philibert of Savoy, defeated the French at St. Quentin. England's entry into the war later that year led to the French capture of Calais, and French armies plundered Spanish possessions in the Low Countries. Nonetheless, Henry was forced to accept a peace agreement in which he renounced any further claims to Italy. The wars ended for other reasons, including the Double Default of 1557, when the Spanish Empire, followed quickly by the French, defaulted on its debts. In addition, Henry had to confront a growing Protestant movement at home, which he hoped to crush.

What nation's army was defeated at the Battle of Marciano?
French