The British Mark IV was introduced in 1917 in time for the Battle of Cambrai where tanks were used in massed formation for the first time. It was a big improvement over the preceding Marks in that it had increased armour and improved guns. The 6 pounders were shortened to stop them from grounding on rough terrain and the Lewis machine guns were standardised as secondary armament. The fuel tank was moved to the rear of the tank to improve safety and for the first time the tank could be driven by just one man instead of three. A total of 1,220 Mk IV were built: 420 Males and 595 Females with 205 Tank Tenders (unarmed vehicles used to carry supplies), making it the most numerous British tank of the war. It remained in British service until the end of the war, and a small number served briefly with other combatants afterwards.