During the majority of the 80's (1980 - 1988), Iran and Iraq were in a conflict called the Iran-Iraq War. By 1990, they still had not achieved a peace treaty, with their war being ended by a UN supported ceasefire. He was expected to return land to Iran, and return the borders to the way they had been. However, two weeks later, Saddam Hussein, the leader of Iraq, delivered a speech in which he accused Kuwait, one of Iraq's neighbors, of taking oil from one of Iraq's largest oil fields. In addition, they began to amass troops on Kuwait's border. On August 2, 1990, Hussein order the invasion of Kuwait, despite negotiations between Iraq and Kuwait.
George H.W. Bush, the current president of the U.S. at the time immediately condemned the invasion, as did the governments of Britain and the Soviet Union. On August 8, 1990, U.S. fighter planes began arriving in Saudi Arabia as part of a buildup plan called Operation Desert Shield (also the name of a 2006 Al-Qaeda attack). In Kuwait, Iraq increased its forces to 300,000 troops.
On November 29th, 1990, the U.N. Security Council authorized the use of force against Iraq if it did not withdraw from Kuwait by the following January. By January, Iraq did not back off, and the coalition forces prepared to face off against Iraq numbered 750,000.
On January 17, 1991, a massive U.S.-led air offensive hit Iraq's air defense, moving onto its communications networks, weapons plants, oil refineries and more. The effort, known as Operation Desert Storm, destroyed Iraqi air forces.
By mid-February 1991, military focus had shifted from air attacks toward Iraqi ground forces in Kuwait and Iraq. A massive allied ground offensive, called Operation Desert Sabre, was launched on February 24. Over the next four days, calition forces encircled and defeated the Iraqis and liberated Kuwait. At the same time, U.S forces attacked Iraq's armored reserves.
On February 28th, George H.W. Bush declared a ceasefire, ending the Persian Gulf War. According to the peace treaty, Iraq would recognize Kuwait's statehood and get rid of its weapons of mass destruction. In the end, 8,000 - 10,000 Iraqi troops were killed, in comparison with only 300 coalition troops.