
Obama, who wants history to remember him as the president who ended a decade of foreign wars, launched a major new escalation in the Middle East, also pledging to bolster Iraqi forces and to increase military assistance to Syria's opposition.
In a prime-time televised address, Obama said that IS, which has beheaded two US journalists and seized a swathe of land in Iraq and Syria, was a uniquely brutal group even by the blood-soaked standards of the Middle East.
"Our objective is clear: we will degrade, and ultimately destroy, ISIL through a comprehensive and sustained counter-terrorism strategy," Obama said, steeling his nation for a new foreign war.
"I have made it clear that we will hunt down terrorists who threaten our country, wherever they are.
"That means I will not hesitate to take action against ISIL in Syria, as well as Iraq," he said, using an alternative acronym for the self-declared Islamic State.
"This is a core principle of my presidency: if you threaten America, you will find no safe haven."
AFP