The enemy of my enemy

There is a wise saying that such a person is my friend. In my lifetime, an example of this was the Soviet Union in WWll. Less than twenty years earlier , Britain was still using military force in an unsuccessful effort to crush the Bolshevik regime, and the Russians were trying to stir up conflict against the British Raj in India. But once the Germans attacked the Soviet Union, the Russians became our allies. We deplore the Syrian government's murderous assaults on many of its citizens. The Obama administration came close to attacking Syria some years ago, chanting "Assad must go. We now have a common enemy , the Islamist extremists known by various names, including Isil. Syria is engaged in a civil war with various rebel groups, ranging from 'Moderates" to Al Qaida affiliates. Instead of trying to reach an understanding with the Syrians that we may seek permission--probably in back channels, because the Syrians would not agree openly to our attacking Isil on Syrian territory-- we brazenly announce that we shall ignore the frontier in order to attack our common enemy. Obama is seeking congressional approval to provide open support to"moderate" rebels. I fear that these "approved" rebels may be more interested in the fight against the Damascus regime than in defeating Isil. I suggest we should concentrate on the one prime and common enemy at a time, quietly working with the enemies of our enemy.