TRAVELING through the chilly landscape around the arctic city of Murmansk, Russia, it becomes clear that this barren region is, a strategic centerpiece in President Vladimir V. Putin’s vast armory. The area around the pole is not divided up among its adjacent states. Its waters are claimed by Russia, as well as by three NATO members: America, Denmark (via Greenland) and Canada. Many of these claims overlap. For the US, ratifying the Law of the Sea would be one splendid pre-emptive strike. Russians and the West should bear in mind how easily political uncertainties can become rigid convictions. Confidence-building measures — treaties, regular dialogue, joint commissions on global challenges — helped defuse one Cold War.The world can’t expect Mr. Putin to take the first steps, so it’s up to America to show sobriety and to avoid giving Russia any pretext for military action.