What rotating military bridge did Leonardo da Vinci design to let troops cross rivers quickly?

Leonardo da Vinci designed a revolving bridge as a rapidly deployable military crossing.

The bridge was intended to swing or pivot into position, allowing an army to cross a river and then clear the passage quickly. Leonardo’s drawings show a lightweight wooden structure supported by a central pivot and counterbalanced for easier handling.

Its value was strategic rather than mechanical novelty alone. A commander could carry the bridge with an army, assemble it near a waterway, and remove it after crossing. This distinguished it from permanent stone bridges and from pontoon bridges, which float on boats or sealed containers.

Leonardo did not build a documented full-size example. His bridge belongs to a group of Renaissance engineering designs that combined practical military needs with careful studies of weight, balance, timber construction, and movement.