At 05:35 Baghdad time on 20 March 2003, US President George W. Bush issued an executive order directing military strikes against Saddam Hussein's regime in Iraq, without an official declaration of war.
US law authorises the president to launch military strikes for reasons related to national security but obliges him to inform Congress within 48 hours of launching any strike. The law also prohibits American forces from staying in a foreign land for more than 60 days without approval of Congress.
Because of this, Bush had to ask Congress officially to approve authorisation to launch the war on Iraq, which he did in 2002.
Congress approved the authorisation in both houses in October 2002, just a month before the midterm elections, with a majority of 296 representatives and an opposition of 133 in the House of Representatives. In the Senate, 77 senators approved the attacks; 23 opposed them.
The vote gave the US military the authorisation to use "all necessary and appropriate force to defend American national security against the constant threat from Iraq and to ensure the enforcement of all UN resolutions related to Iraq."