GOING TO WAR WITH THE COMMANDER WE'VE GOT:

The refusal to authorize force would be taken as an ideological pivot point. Nations such as China, Russia and Iran would see this as the triumph of a political coalition between the peace party of the left and the rising isolationists of the right. And they would be correct. The strategic calculations of every American enemy and friend would be adjusted in ways that encourage challenge and instability. Prime Minister David Cameron's recent loss of the vote authorizing military action -- the first such repudiation since 1782 -- has weakened Britain as an actor in the world. America should refuse to follow it down.

I would prefer to defend a form of internationalism less conflicted and hesitant than President Obama's. But even so, it is better than the alternative of seriously compromising the credibility of the presidency itself. And those who claim that this credibility has already reached bottom are lacking in imagination.

Follow @brothersjudd