Ryan Cooper:

Open conflict between Russia and the United States is heating up in Syria. After American forces shot down a Syrian fighter jet, Russia suspended use of an Obama-era communications line used to prevent collisions and conflict, and threatened to shoot down American planes.

America's Syria policy was and continues to be absolutely moronic. But this alarming development is also a reminder that there is simply no alternative to diplomatic engagement with Russia, the world's only other nuclear superpower. That's something both the American military, and liberals fired up over Trump's Russia scandal, would do well to remember.

...

Russia has a clear goal: prop up the Assad regime, but avoid being drawn too far into the conflict. America is, as far as anyone can tell, fighting ISIS, attempting regime change without invasion, arming some rebels but fighting others, and trying to help Kurdish militia without annoying Turkey too much. Both Trump and the foreign policy establishment... childishly refuse to admit that most of these goals are incompatible with one another.