Designed for Duke Sforza, Leonardo da Vinci’s revolving bridge could be quickly packed up and transported for use by armies on the move to pass over bodies of water.
The bridge would swing across a stream or moat and set down on the other side so that soldiers could pass with little trouble. The device had wheels and incorporated a rope-and-pulley system for both quick employment and easy transport. It was also equipped with a counterweight tank for balancing purposes.
Da Vinci described the bridge in his notes as being "light yet rugged" and it was one of several bridges he designed for the Duke in his lifetime. Another, similar bridge Leonardo da Vinci built for armies was a fast-construction bridge that made it quicker and easier for soldiers to cross multiple rivers.
Such temporary bridges helped armies to navigate unfamiliar terrain with less difficulty, and more easily escape from pursuing forces. They also provided armies with what da Vinci believed was one of the most important aspects of warfare: mobility.