text: In 1481, being discontented with his progress in Florence, he left for Milan.\nAgain came the thrust of war and again Leonardo's inventions poured from his fertile brain.\nIn a letter to the Duke of Milan he said he would build him "safe" unassailable covered wagons with artillery". Tank warfare to be "invented" in the 1914-1918 war had been invented. \nHe also invented for the Duke's use an explosive shell - shrapnel - poison gas and a protective gas mask, but once again was laughed at.\nAfter the war had receded Leonardo also invented a spinning machine, a look, a needle-sharpening machine and a metal rolling mill but his patron the Duke had no interest in machinery. He gave Leonardo a commission to paint a picture on one of the bare while walls of the refectory of the Church of Santa Maria delle Grazie. When it was finished it was the immortal "Last Supper".\nIn 1499 the French King Louis XII conquered Milan and Leonardo left for Venice. He arrived just as the Turks had defeated the Venetians at Lepanto and Turkish warships were threatening the city itself.\nThe council of Venice, having heard of Leonardo's ideas of military weapons consulted him about the defence of the city and almost overnight this ever amazing genius invented the submarine and the diving suit.\nThen, for some reason which has never been explained, Leonardo left Venice before either of his inventions could be used and returned to Florence.\nAgain came war, for Cesare Borgia, Prince of Romagna, decided to enlarge his principality by the simple expedient of absorbing his neighbouring states. To this end he invited Leonardo to become his military engineer, giving him the rank of a general.\nAfter two years, however, Leonardo returned to Florence which had become involved in war with Pisa.\nHe was again consulted and this time his mighty brain envisaged a scheme which was as fantastic as was devastating. \n\nThere's a whole lot more on the site