The U.S. does not have the force posture capable of resisting a Russian invasion of eastern Ukraine. Putin knows this. As such, he will test President Trump early in his administration. Trump will likely make a deal with Putin in the near-term for concessions here. But, I suspect, once President Trump completes his military expansion and force modernization, he will begin fully resisting Russian aggression. Time and resolve, therefore, is the best answer to Russian revanchism.