Question

Why did the US support Iraq during the Iran-Iraq war?

Answer 1

The short answer is that the US viewed Iran as a hostile country and vice-versa. The Iranian Revolution had not only taken American hostages in the late 70s, but it had also put into power an extremely hostile regime under the Ayathollah Khomeni that had gone to far as to call the US "the Great Satan". There was no question that Iran hated the US' guts under Khomeni and as the old saying goes, the enemy of my enemy is my friend.

The longer answer involves Cold War politicking. The Soviets were keen on keeping Iraq as a weapons customer and the US wanted to leverage Iraq as far away from Soviet influence in supplying them with technical weapons information (such as chemical weapons) and intelligence. The US also wanted to protect a number of their interests in the region from a potential Iranian hegemony, so protecting those interests had also become another reason for supporting Iraq as a fair weather friend during the Cold War.