Relations with Iraq had never been good historically; however, they took a turn for the worse in 1980, when Iraq invaded Iran. The stated reason for Iraq's invasion was the contested sovereignty over the Shatt al-Arab waterway ("Arvand Rud" in Persian). Other reasons, unstated, were probably more significant: Iran and Iraq had a history of interference in each other's affairs by supporting separatist movements, and although this interference had ceased since the Algiers Agreement (1975), after the Revolution Iran resumed support for Kurdish guerrillas in Iraq.