Leonardo’s letter to Ludovico il Moro assured him:
When a place is besieged I know how to cut off water from the trenches and construct an infinite variety of bridges, mantlets and scaling ladders, and other instruments pertaining to sieges. I also have types of mortars that are very convenient and easy to transport…. when a place cannot be reduced by the method of bombardment either because of its height or its location, I have methods for destroying any fortress or other stronghold, even if it be founded upon rock. ….If the engagement be at sea, I have many engines of a kind most efficient for offence and defence, and ships that can resist cannons and powder.
In Leonardo’s notebooks there is an array of war machines which includes a vehicle to be propelled by two men powering crank shafts. Although the drawing itself looks quite finished, the mechanics were apparently not fully developed because, if built as drawn, the vehicle would never progress in a forward direction. In a BBC documentary, a military team built the machine and changed the gears in order to make the machine work. It has been suggested that Leonardo deliberately left this error in the design, in order to prevent it from being put to practice by unauthorized people. Another machine, propelled by horses with a pillion rider, carries in front of it four scythes mounted on a revolving gear, turned by a shaft driven by the wheels of a cart behind the horses.
Leonardo’s notebooks also show cannons which he claimed “to hurl small stones like a storm with the smoke of these causing great terror to the enemy, and great loss and confusion.” He also designed an enormous crossbow. Following his detailed drawing, one was constructed by the British Army, but could not be made to fire successfully. In 1481 Leonardo designed a breech-loading, water cooled cannon with three racks of barrels allowed the re-loading of one rack while another was being fired and thus maintaining continuous fire power. The “fan type” gun with its array of horizontal barrels allowed for a wide scattering of shot.
Leonardo was the first to sketch the wheel-lock musket c. 1500 AD (the precedent of the flintlock musket which first appeared in Europe by 1547), although as early as the 14th century the Chinese had used a flintlock ‘steel wheel’ in order to detonate land mines.
While Leonardo was working in Venice, he drew a sketch for an early diving suit, to be used in the destruction of enemy ships entering Venetian waters. A suit was constructed for a BBC documentary using pigskin treated with fish oil to repel water. The head was covered by a helmet with two eyeglasses at the front. A breathing tube of bamboo with pigskin joints was attached to the back of the helmet and connected to a float of cork and wood. When the scuba divers tested the suit, they found it to be a workable precursor to a modern diving suit, the cork float acting as a compressed air chamber when submerged. His inventions were very futuristic which meant they were very expensive and proved not to be useful.