Realists are in broad agreement that the United States is overcommitted there. Indeed, the fact that the U.S. military remained in Europe after the end of the Cold War seems profoundly at odds with realism’s assumption that alliances are primarily a response to threat. But whether bureaucratic politics or simple path dependence are to blame, the fact is that, 30 years after the collapse of the Soviet Union, the United States is still largely responsible for protecting Europe. And the geographic scope of the commitment has expanded to encompass all of the former Warsaw Pact countries.

Ten years from now, the United States should have no significant troop presence in Europe.

Realists are in broad agreement that the United States is overcommitted there. Indeed, the fact that the U.S. military remained in Europe after the end of the Cold War seems profoundly at odds with realism’s assumption that alliances are primarily a response to threat. But whether bureaucratic politics or simple path dependence are to blame, the fact is that, 30 years after the collapse of the Soviet Union, the United States is still largely responsible for protecting Europe. And the geographic scope of the commitment has expanded to encompass all of the former Warsaw Pact countries.

As a result, NATO’s membership has doubled. The United States currently has around 100,000 troops stationed in Europe. Troop levels increased after the start of the war in Ukraine in 2022, but even in more normal times, the U.S. troop commitment to the continent has hovered between 50,000 and 75,000. Existing base structures—and the slowly dying Treaty on Conventional Armed Forces in Europe—keep the majority of U.S. personnel based in Germany, Italy, and the United Kingdom, but growing numbers are now stationed in Eastern European states on a rotational (but, in practice, permanent) basis.

Perhaps more important than the raw number of troops is United States’ role as a technological and logistical enabler for European forces, which often lack key capabilities in intelligence, surveillance, and reconnaissance (ISR); airlifting; or refueling. The Libya intervention in 2011 is perhaps the clearest example of U.S. centrality to European force projection; though initially intended to play the primary role in the intervention, European forces were not able to sustain operations alone. The United States ended up providing ammunition, air-to-air refueling, and significant intelligence support. As one observer at the time put it, “Europe flew the planes and attack helicopters, but most of the time they were firing U.S. munitions at targets identified by the U.S., in operations coordinated by U.S.