The best way to introduce the machines that Leonardo designed for war is with is own words, taken from his own letter to Ludovico il Moro: "I have plans for bridges very light and strong and suitable for carrying very easily advancing troops and allowing the enemy forces to flee. […]. I have plans for destroying every fortress or other stronghold unless it has been founded upon rock. […] I have also plans for making cannon, very convenient and easy of transport , with which to hurl small stones in the manner almost of hail, which can raise up a small storm, causing such enormous amounts of smoke as to strike fear into the heart of the enemy, creating great damage and confusion".