Remember Afghanistan? The longest war in American history? Ever? When it comes to wars, we Americans have a selective memory. The Afghan war, dating from October 2001, has earned the distinction of having been forgotten while still underway. President Trump’s Inaugural Address included no mention of Afghanistan. Nor did his remarks last month at a joint session of Congress. For the new commander in chief, the war there qualifies at best as an afterthought — assuming, that is, he has thought about it all. A similar attitude prevails on Capitol Hill. Congressional oversight has become pro forma. Last week Gen....