The United States military got involved in the Persian Gulf in 1990-1991 due to the invasion of Kuwait.
Saddam Hussein, the lead of Iraq, order to invasion and occupation of Kuwait. He claimed that this country belonged to Iraq previously and should still be under their control. This invasion was uncalled for and was based on faulty logic. After this invasion, the United Nations and the US took action, as they did not want to allow aggression to take place in the Middle East.