What tensions existed between Iran and Iraq? What effect did this have on the oil market?

Tensions had existed between the countries for some time. Khomeini felt he had been mistreated in Iraq during his exile there and held Saddam Hussein responsible. Hussein felt threatened by Iranian agitation, thinking that some of his own citizens might join forces with the Iranians. The oil infrastructure was near a shared waterway and about 4 million barrels were taken off the world market each day because of the conflict.