Collective security, the official goal of NATO, the North Atlantic Treaty Organization, seems plausible on its face. A group of nations ostensibly concerned about a common threat agree to defend one another in the event of an attack. "All for one and one for all," as the Three Musketeers said. But like many things, the principle, even if sincerely invoked, is more problematic than the first glance indicates. This is particularly true with governments, and in no area more so than foreign policy and armed forces. Schoolyard analogies involving bullies do not hold. NATO was established soon...