The Shatt al-Arab, or Arvandrud in Persian, provides Iraq with its only means of access to the Persian Gulf. Issues of joint sovereignty over the waterway have long been a source of contention between Iran and Iraq. In 1975 Mohammad Reza Shah Pahlavi of Iran and Vice President Saddam Hussein of Iraq signed the Algiers Agreement, which demarcated the thalweg (middle) line along the Shatt al-Arab as the border between the two states. In September 1980 Iraq launched an offensive against the Islamic Republic of Iran, declaring one of its intentions to be the restoration of the Shatt al-Arab to sole Iraqi sovereignty. Hostilities were brought to an end in 1988, but a peace agreement remains to be signed between the two countries. UN Resolution 598 has not been implemented other than to establish a cease-fire; sovereignty of and navigation rights in the Shatt al-Arab remain unresolved. Since Iraq's massive defeat at the hands of the United States in the Gulf War of 1991, borders have reverted to the 1975 demarcations, albeit unofficially.
see also algiers agreement (1975).
Sirriyeh, Hoseyn. "Development of the Iraqi–Iranian Dispute, 1847–1975." Journal of Contemporary History 20, no. 3 (1985): 483–492.