U.S.-Iran Hostilities during the Iran-Iraq War

The Tanker War and US military involvement
Starting in 1981, both Iran and Iraq attacked oil tankers and merchant ships, including those of neutral nations, in an effort to deprive the opponent of trade. After repeated Iraqi attacks on Iran's main exporting facility on Khark Island, Iran attacked a Kuwaiti tanker near Bahrain on May 13 1984, and a Saudi tanker in Saudi waters on May 16 (both Kuwait and Saudi Arabia being members of GCC supported Saddam during the war). Attacks on ships of noncombatant nations in the Persian Gulf sharply increased thereafter, and this phase of the war was dubbed the "Tanker War."

Tanker War
Lloyd's of London, a British insurance market, estimated that the Tanker War damaged 546 commercial vessels and killed about 430 civilian mariners. The largest of attacks were directed by Iran against Kuwaiti vessels, and on November 1 1986, Kuwait formally petitioned foreign powers to protect its shipping. The Soviet Union agreed to charter tankers starting in 1987, and the United States offered to provide protection for tankers flying the U.S. flag on March 7 1987 (Operation Earnest Will and Operation Prime Chance). Under international law, an attack on such ships would be treated as an attack on the U.S., allowing the U.S. to retaliate militarily. This support would protect ships headed to Iraqi ports, effectively guaranteeing Iraq's revenue stream for the duration of the war.

Attack on USS Stark
An Iraqi plane attacked the USS Stark (FFG 31), a Perry class frigate on May 17, killing 37 and injuring 21. But U.S. attention was on isolating Iran; it criticized Iran's mining of international waters, and in October 1987, the U.S. attacked Iranian oil platforms in retaliation for an Iranian attack on the  U.S.-flagged Kuwaiti tanker Sea Isle City.

Operation PRAYING MANTIS
On April 14, 1988, the frigate USS Samuel B. Roberts was badly damaged by an Iranian mine. U.S. forces responded with Operation PRAYING MANTIS on April 18, the United States Navy's largest engagement of surface warships since World War II. Two Iranian ships were destroyed, and an American helicopter was shot down, killing the two pilots.

The USS Vincennes incident
In the course of these escorts by the U.S. Navy, the cruiser USS Vincennes shot down Iran Air Flight 655 with the loss of all 290 passengers and crew on July 3 1988. The American government claimed that the airliner had been mistaken for an Iranian F-14 Tomcat, and that the USS Vincennes was operating in international waters at the time and feared that it was under attack. The Iranians, however, maintain that the Vincennes was in fact in Iranian territorial waters, and that the Iranian passenger jet was turning away and increasing altitude after take-off. U.S. Admiral William J. Crowe also admitted on ABC's Nightline that the Vincennes was inside Iranian territorial waters when it launched the missiles. The U.S. eventually paid compensation for the incident but never apologized.

According to the investigation done by Ted Koppel, during the war, U.S. navy used to set decoys inside the Persian Gulf to lure out the Iranian gunboats and destroy them, and at the time USS Vincennes shot down the Iranian airline, it was performing such an operation. U.S. Navy personnel have criticized the Nightline report as being a sensationalized version of the events.