Unfortunately, Leonardo’s painting commission for the Palace of the Signoria was never completed. By the end of the year 1478, the Pope, angered by the killing of the Archbishop during the Pazzi conspiracy, had declared war on the Republic of Florence. Ferdinand, the King of Naples, was persuaded to help in this war against Florence and the Medicis. As the papal forces were approaching the fortresses on the Florentine hills, the Council of Florence discontinued Leonardo’s commission in order to conserve money for the defense of the city. Disappointed though he was, Leonardo did not allow this setback to discourage him. From a page of drawings in the Uffizi Gallery of Florence on which are sketched various arms and war materials, we learn that he turned from his artistic to his mechanical skills and began designing engines of war. Besides being a Florentine concerned with the defense of his city, Leonardo was eager to gain an appointment with Lorenzo as military engineer to make up for the painting commission he had just lost. Also, as the fifteenth century was a turning point in the methods of waging war, Leonardo was attracted to all the mechanical possibilities of the new artillery. Before then soldiers had used spears, bows and arrows, and stone-throwing catapults, among other primitive methods. One of Leonardo’s designs included a light cannon whose barrel could be raised or lowered to proper elevation by means of a hand-cranked screw and whose horizontal direction could be determined by a maneuverable cradle. The military appointment that Leonardo hoped for didn’t come. Unfortunately for the Medicis, the war with the papal forces was being lost. One by one, the fortresses under siege surrendered; more and more of the Florentine troops were fleeing. Leonardo continued the work on his military machines for, although he was having some success painting Madonnas for private homes and had even received a commission from the King of Portugal for a tapestry design, he still wanted official recognition for his inventions from Lorenzo de’ Medici. During these weeks late in the year of 1479, Leonardo conceived many ingenious devices to wage war. Besides the small artillery piece, he designed a _bombard_, or rock-throwing cannon, which did not recoil when it was fired. This was followed by a light gun arranged in three tiers of barrels, mounted so that while one tier was fired, the second was being loaded and the third was cooling (a forerunner of the modern machine gun). Another was a device to repel enemy ladders. It consisted of a horizontal beam laid parallel to the top of a fortress wall; the beam could be pushed outward by one man or several men using a system of pulleys. [Illustration: _Leonardo’s design for a machine gun. It had thirty-three barrels in three banks of eleven each. While one bank was fired, one cooled and the other was reloaded._]