There were many reasons for Iran-Iraq war. Besides territorial disputes, the 1979 revolution of Iran and the US and her allies’ hostility are the most important. Mr. Khomeini and his team wanted to spread their revolution around the Islamic world. They eyed two closest neighbours, Iraq and Pakistan to export their revolution and parties were created there by the Shiites. They revolted firs in Iraq which Saddam Husain had to suppress with power. This naturally enraged Iranian revolutionists. The US and her allies were already angry over the overthrown of the govt. of Raza Shah, their the then best ally and trust worthy person in the oil-rich region. They provoked and encouraged Saddam to invade Iran, assuring their full material and moral support. Saddam too realising the future threat advanced an attack giving the reason the custody of Shatt-al-Arab. The war lasted eight years because the big powers wanted so. Finally both the parties realised the situation and agreed to end the war. It was the time when Soviet Union has already reached to a complete defeat in Afghanistan and had no courage to play any role in the world politics.