The tanker war seemed likely to precipitate a major international incident for two reasons. First, some 70 percent of Japanese, 50 percent of West European, and 7 percent of American oil imports came from the Persian Gulf in the early 1980s. Second, the assault on tankers involved neutral shipping as well as ships of the belligerent states.

The tanker war had two phases. The relatively obscure first phase began in 1981, and the well-publicized second phase began in 1984. As early as May 1981, Baghdad had unilaterally declared a war zone and had officially warned all ships heading to or returning from Iranian ports in the northern zone of the Gulf to stay away or, if they entered, to proceed at their own risk. The main targets in this phase were the ports of Bandar-e Khomeini and Bandar-e Mashur very few ships were hit outside this zone. Despite the proximity of these ports to Iraq, the Iraqi navy did not play an important role in the operations. Instead, Baghdad used Super Frelon helicopters equipped with Exocet missiles or Mirage F-1s and MiG-23s to hit its targets.

In March 1984, the tanker war entered its second phase when an Iraqi Super Etendard fired an Exocet missile at a Greek tanker south of Khark Island. Until the March assault, Iran had not intentionally attacked civilian ships in the Gulf. The new wave of Iraqi assaults, however, led Iran to reciprocate. In April 1984, Tehran launched its first attack against civilian commercial shipping by shelling an Indian freighter. Most observers considered that Iraqi attacks, however, outnumbered Iranian assaults by three to one.

Iran's retaliatory attacks were largely ineffective because a limited number of aircraft equipped with long-range antiship missiles and ships with long-range surface-to-surface missiles were deployed. Moreover, despite repeated Iranian threats to close the Strait of Hormuz, Iran itself depended on the sea-lanes for vital oil exports. Nonetheless, by late 1987 Iran's mine-laying activities and attacks on ships had drawn a large fleet of Western naval vessels to the Gulf to ensure that the sea-lanes were kept open.

Data as of December 1987