Obama's best shot at a foreign policy legacy is reviving NATO

NATO also needs to become a lot clearer about its goals. Europe has two immediate security issues: the threat from Russia in the east, and the threat from Islamic fundamentalism to the south. NATO therefore needs two command centers, each of which takes care of planning and intelligence for defense against those threats. The basing of troops and equipment needs to be rethought completely: If we were starting from scratch, nobody would put them where they are now. NATO needs to shut down unnecessary commands and legacy bases, and move on.

At the same time, NATO members should understand that any further enlargement is not charity work: Every time the NATO membership is extended to another state, current members have to be prepared to defend that state—and if they aren’t, then the enlargement should be stopped. Either Article 5 is an absolute guarantee, or it is worthless.

Once NATO has become clearer about its real security interests, its forces can again start carrying out annual exercises, as they did during the Cold War. It’s time to rehearse our reaction to a Crimean-style Russian invasion of Latvia, led not by regular troops but by “little green men” pretending to be local Russians.