It was the oddest of meetings between a U.S. President and another countries leader I think I ever saw. I don't know what the facts are about Germany's dept to NATO or the U.S. but we must never falter on defending NATO’s most exposed and vulnerable allies—that would potentially be inviting a devastating war, rather than deterring it. The U.S. is the leader of the Atlantic alliance and has an indispensable role in making its collective deterrent sufficiently robust and credible.