OBAMA'S WAR

How Obama could be the first president to wage a war that Congress hasn't backed 

The U.S. Constitution grants Congress the sole authority to declare war, and there is no precedent for a U.S. president unleashing American military might after Congress refuses to endorse it. 

But few occupants of the White House have bothered to seek the legislative branch's permission in advance for the entirety of what they were doing with U.S. armed forces.

President Truman engaged U.S. forces in a conflict in South Korea without Congress by arguing that it was a 'police action' authorized by the United Nations.  That produced more than 54,000 American casualties.

John F. Kennedy sent U.S. troops to Vietnam in 1961 and increased that number in 1962, however they were (supposedly) sent there as military advisors only.

Lyndon Johnson used the 1964 Gulf of Tonkin Resolution, a narrowly drawn permission slip for responses to a handful of minor naval skirmishes, to justify the entire Vietnam War.

George W. Bush premised the Gulf War on weapons of mass destruction that Iraqi dictator Saddam Hussein was supposed to have possessed.  He had the approval of Congress, however Congress ultimately grew wearier of funding that war as evidence of the weapons failed again and again to materialize.

When Ronald Reagan sent U.S. Marines into Grenada in 1983, the rationale he gave Congress was that armed conflicts in the island nation were jeopardizing the safety of American medical students.

Bill Clinton sent U.S. forces into Somalia in 1992 with a non-combat humanitarian mission.  By 1994 the country's civil war had grown to encompass areas where American troops were stationed, and they were all withdrawn.  Congress had a chance to authorize a military mission, but the House and Senate fought over competing versions of a resolution and it never made it to Clinton's desk.

Clinton's 1999 air strikes against Serbia were justified at the time with a somewhat dubious claim that he was participating in a NATO mission to save the lives of ethnic cleansing victims in Kosovo.

Just two years ago, Barack Obama leveraged a resolution from the United Nations – not Congress – to back his decision to order bombing raids of Libya.

On a few occasions, members of Congress have given their assent after a president has boxed them in by taking action on his own.

In 1846, for instance, President James Polk sent troops to the Mexican border without consulting Congress, in order to muscle Mexico into selling Texas to the U.S.  Congress later authorized a declaration of war, but only after a small contingent of Mexican army regulars crossed the U.S. border and massacred American troops who went to investigate.