evidence: Taking advantage of the confusion and chaos surrounding the change of power there, Saddam Hussein’s regime hoped to fill the regional power vacuum that had been created. Baghdad also had set its sights on the conquest of Khuzestan – an ethnically Arab province of Iran, bordering on the Iraqi province of Basra and the Persian Gulf – and on regaining full control over the Shatt al-Arab (after the humiliation of the 1975 Algiers Treaty), which would eliminate Iraq’s landlocked situation. [...] An immediate cause of the war was the long-standing question of sovereignty over the Shatt al-Arab (in Arabic), or Arvand-Rud (in Persian). The 200-kilometre-long waterway, of which the last 80 kilometres form the frontier between Iran and Iraq, is strategically important for both countries, because Basra, the only Iraqi port with access to the Persian Gulf, lies upstream, and both countries have oil installations near the waterway. Iraq and Iran had engaged in border clashes for many years but reached an agreement in 1975 in Algiers, before Saddam Hussein in late August 1980 issued an ultimatum demanding that Iran grant Iraq sovereignty over the Shatt al-Arab. When the ultimatum expired without a reaction by the Iranian government, Iraqi troops invaded Iran.