On September 15, 1916, British Mark I tanks went into action for the first time, at Flers-Courcelette during the Somme offensive. Forty-nine had been shipped to France and about 32 managed to start and move toward the German lines. Only nine got through to do what had been asked of them. Courcelette and Flers were taken.
The machine had been built to solve one specific problem: a trench system protected by barbed wire and machine guns, behind which artillery could not be advanced, and across which infantry could not move without appalling losses. The answer was a vehicle that could not be stopped by wire, could cross a shell crater and a trench, and carried guns. The caterpillar track did that by spreading the weight: the Mark I weighed around 28 tons and had a ground pressure low enough to cross broken ground. It had no suspension and no radio. The crew of eight worked in a compartment full of engine noise and fumes, at over 40 degrees. The steering needed four men.
The programme was pushed by Winston Churchill at the Admiralty, who set up the Landships Committee in 1915 on the argument that the navy should build armoured vehicles. The secrecy was total. Workers were told they were making water carriers for Mesopotamia, which is where the word tank came from and why it stuck. The first prototype, Little Willie, ran in September 1915; the design that went to France was by William Tritton and Walter Gordon Wilson.
Haig had wanted hundreds and got dozens, and the decision to use them on September 15, at the tail of a four-month offensive, was made over the objections of the tank corps' own commanders, who said the ground was too broken and there were not enough machines. They were right. The tanks were mechanical wrecks by the second day.
What made it matter anyway was the reaction. German troops who had never seen one surrendered to them, and reports from the front describe panic. Within a year the French had the Renault FT, which set the shape every tank has followed since: a rotating turret, a driver at the front, an engine at the back. By 1918 the British were using more than 500 at once at Amiens, and the German general staff wrote afterwards that the tanks, not the artillery, were what broke the army's morale.