The development of tanks in World War I was a response to the stalemate that had developed on the Western Front. Although vehicles that incorporated the basic principles of the tank (armour, firepower, and all-terrain mobility) had been projected in the decade or so before the War, it was the alarmingly heavy casualties of the start of its trench warfare that stimulated development. Research took place in both Great Britain and France, with Germany only belatedly following the Allies’ lead.
The first tanks were mechanically unreliable. There were problems that caused considerable attrition rates during combat deployment and transit. The heavily shelled terrain was impassable to conventional vehicles, and only highly mobile tanks such as the Mark and FTs performed reasonably well. The Mark I’s rhomboid shape, caterpillar tracks, and 26-foot (8 m) length meant that it could negotiate obstacles, especially wide trenches, that wheeled vehicles could not.