- Vladimir] Putin's aggression makes the possibility of a war in Europe between nuclear-armed adversaries frighteningly real, - writes Kimberly Marten in a new Council Special Report on tensions between Russia and the North Atlantic Treaty Organization (NATO). She outlines how U.S. policymakers can deter Russian aggression with robust support for NATO, while reassuring Russia of NATO's defensive intentions through clear words and actions based in international law.

Marten, a professor of political science at Barnard College, Columbia University, and director of the...