From the mid-1930s through the Cold War, Europe was critical to U.S. strategic thinking, which developed around the assumption that foreign domination of Europe was inimical to U.S. national security. With the end of the Cold War, the United States sought to forge a Europe that was “whole and free.” However, since Putin has returned to office, he has launched a determined effort to reassert Moscow’s influence in areas formerly under Soviet control. Russia’s objective is to overturn the European security order that emerged after the end of the Cold War. As Russia continues to invest aggressively in modernizing its military, many NATO countries continue to pursue policies of disarmament, divest themselves of key capabilities, and struggle to meet NATO’s 2 percent of GDP defense spending requirement. Europe’s political disunity, lack of leadership, and absence of appetite for confrontation with Russia, as well as the weakest United States military presence in Europe since World War II, allow the Kremlin to exploit its growing military capabilities along its periphery. The dwindling presence of NATO forces is now running the risk of failing to deter Russian aggression.