It was in the Middle East that the Chieftain was to see all of its operational experience. First, it was used extensively by Iran during the Iran–Iraq War of 1980–88, including the largest tank battle of the war, with mixed results as the Chieftain Mk 3/5 suffered from chronic engine problems and low power-to-weight ratio, making it unreliable and slow when manoeuvring over harsh terrain, which in turn made it prone to breakdowns in the midst of battle or a sluggish target and thus vulnerable to enemy tank fire. Out of the 894 Chieftain tanks that had started the war only 200 were left by the wars end.