What rotating mechanical bridge did Leonardo da Vinci design to let armies cross rivers quickly?

Leonardo da Vinci designed a revolving bridge that could be rotated into position for rapid military crossings.

The bridge was intended to combine portability with speed. A central arrangement of supports and a rotating structure would allow troops to move the bridge across a waterway and then swing it into alignment. Leonardo’s military engineering studies repeatedly focused on equipment that could be transported, assembled, and removed quickly.

A revolving bridge differs from a drawbridge, which pivots upward to block or open a passage, and from a swing bridge, a later term generally associated with bridges that rotate horizontally around a central pivot. Leonardo’s design belongs to the broader history of temporary military bridges rather than modern permanent bridge construction.

The bridge is best understood as a proposed mechanism preserved in Leonardo’s drawings. There is no reliable evidence that Leonardo built a full-scale operational version, but the design demonstrates his interest in combining structural support with controlled rotation.