WASHINGTON // President Barack Obama's decision to seek authorisation from Congress before striking Syria is a rare example of the White House ceding ground to the legislative branch of government.
While the US Constitution gives Congress the power to declare war, the last time that a formal declaration was adopted was in 1941, when the United States entered World War II.
Since then, a succession of American presidents have unilaterally initiated military strikes or land invasions on numerous occasions without congressional approval, invoking their constitutional authority as commander in chief.
The War Powers Resolution of 1973, initiated in response to the deeply unpopular Vietnam War, in theory requires the president to seek authorisation from lawmakers for any military intervention lasting beyond 60 days.
President George W. Bush sought and received authorisation under the resolution before launching the invasion of Iraq in 2003.
But most presidents have acted as if the 1973 act, which president Richard Nixon unsuccessfully attempted to veto, is unconstitutional.
In December 1995 for example, president Bill Clinton ordered the deployment of 20,000 troops in support of the Nato peacekeeping force in Bosnia-Herzegovina following the Dayton Peace Accords.
Clinton's decision came despite Congress's failure to agree on several draft resolutions supporting or prohibiting the intervention.
Clinton ordered air strikes without congressional approval in 1999, hitting Yugoslavia for 78 days in the Kosovo conflict.
Military operations in Somalia (1992) and Haiti (1994) also took place without congressional approval, as well as cruise missile strikes on Afghanistan and Sudan in 1998 following the twin bombings of US embassies in Kenya and Tanzania.
More recently in March 2011, Mr Obama justified military intervention in Libya on the grounds of a UN Security Council resolution despite Congress' request that it be consulted.