Bastion fortifications were further developed in the late fifteenth and early sixteenth centuries, primarily in response to the French invasion of the Italian peninsula. The French army was equipped with new cannon and bombards that were easily able to destroy traditional fortifications built in the Middle Ages. Star forts were employed by Michelangelo in the defensive earthworks of Florence, and refined in the sixteenth century by Baldassare Peruzzi and Vincenzo Scamozzi. The design spread out of Italy in the 1530s and 1540s.