Question

When President George W. Bush ordered the invasion of Iraq to overthrow Saddam Hussein in 2003, he took a unilateral military action. His stated purpose was to increase US national security. Presidents Clinton and Obama favored more multilateral efforts when intervening in countries such as Kosovo and Libya. Is there a justification for the US to engage in unilateral rather than multilateral military action overseas?

Answer 1

A unilateral purpose takes less time, however takes all the blame.  
When a state is threatened it may feel that a reason is good enough to go at it alone.