When Sforza was overthrown in 1500, Leonardo fled Milan for Venice, which was at war with the Ottoman Empire. He approaches the Senate of the Republic and offers his services as an engineer. Leonardo, still fascinated by the flow of water and its power, wanted to build a movable dam that would allow the Venetian forces to lure the Turks into the valley of the Isonzo River, then flood it, wiping out enemy forces. He also designed a system of movable barricades to protect the city from attack. The Senate did not follow through with its plans, citing the immense cost. He also designed a diving device and wanted to launch an underwater raid on the Ottoman fleet, drilling holes in the bottom of their ships. Its design was remarkably similar to modern diving equipment. This plan was also not carried out, but Leonardo was careful to keep the details of his designs a secret so that they did not fall into the wrong hands.
In Cesena in 1502, Leonardo entered the service of Cesare Borgia, the son of Pope Alexander VI, acting as an architect and military engineer, traveling through Italy with his patron. Leonardo first created a map to attack Imola, Cesare Borgia’s stronghold. Seeing him, Borgia hired him there as his chief military engineer and architect. Leonardo’s diaries include a large number of inventions, both practical and impractical. They also included a mechanical knight, hydraulic pumps, finned mortar shells, and even a steam cannon.
Although credit for inventing the first practical parachute dates back to 1783, Leonardo conceived the idea hundreds of years earlier. He made a sketch of the invention with this accompanying description: “If a man has a linen tent that has all the openings closed and it measures twelve braccia (about 23 feet) in diameter and twelve braccia. depth, he will be able to throw himself from any height without suffering injury. A braccia is about two feet tall.