Republicans and other critics of the president have alleged that Obama went to Congress with the decision on whether or not to punish Syria for the use of chemical weapons because his hand was weak and he sensed eminent defeat. I contend that it is not as simple as that. When it comes to foreign policy Obama is a multilateralist--he does not hold with unilateralism, particularly in the use of military force, and he is not a believer in American exceptionalism. As both Russia and China were likely to veto an authorization for the use of force in the UN Security Council, Obama was left with two possible venues for multilateral action: NATO and the Arab League. NATO provided the authorization and the force for the campaign against Serbia over Kosovo in 1999. But Kosovo is in Europe not the Middle East. NATO's Atlantic Treaty covers Europe and the North Atlantic region between North America and Europe--it does not cover the Middle East.
This left the Arab League, the organization that provided the authorization for Western force against Muammar Gaddafi in Libya in 2011. Then it was individual NATO countries, primarily France, Britain and the United States, that provided the outside force in the form of air cover for the opposition rebels. But the Arabs are divided about Syria and wary of providing a precedent for Western intervention in Arab internal affairs. Libya was an exception, because Gaddafi had made so many enemies in the Arab world over the decades. And even if the Arab League were to vote to authorize force against the Assad regime, the vote in the British parliament not to authorize such force would have left the United States alone with France to provide it. While physically the United States Navy is capable of firing enough cruise missiles on its own that it does not need assistance from France or even the U.S. Air Force, more political backing from Western allies would be useful.
So Obama has decided to hold a debate on the issue in Congress. This will give him a chance to make his case not just to the Congress but also to his allies. He can wait until the UN inspectors have issued their report and present his evidence to Congress. If, and this is a big if at present, he wins authorization from Congress, he will be in a better position to request it from his European allies and possibly David Cameron could even request a second vote in the House of Commons. If not, Obama can then deflect the blame to Congress.