The Mark I was the world's first tank, a tracked, armed, and armoured vehicle, to enter combat. The name "tank" was initially a code name to maintain secrecy and disguise its true purpose by making it appear to be a water transport vehicle for bringing water to the troops at the front line.[2] The tank was developed in 1915 to break the stalemate of trench warfare. It could survive the machine gun and small-arms fire in "No Man's Land", travel over difficult terrain, crush barbed wire, and cross trenches to assault fortified enemy positions with powerful armament. Tanks also carried supplies and troops. Credit Wikipedia

1 for right cannon
2 for left cannon