The role of the U.S. military—and of U.S. alliances—is more controversial now than it has been for several decades. 

Of the more than two million U.S. military personnel today, over 228,000 are stationed in foreign countries, with the largest contingents based in Germany, Japan, and South Korea. The U.S. Navy also has more than a dozen permanent installations abroad, including in the Americas, Europe, the Indo-Pacific, and the Middle East.

Advocates of a large military footprint say it keeps adversaries at bay (including China, Iran, North Korea, Russia, and various terrorist groups), protects allies and the flow of free trade, and ensures the United States maintains an unrivaled influence on the world stage. Critics, meanwhile, say that the U.S. military budget of more than $800 billion—far more than any other country—is too high, and that recent presidents have gained too much control over the decision to use military force, which they say is the responsibility of Congress.

U.S. defense strategy is now focused on great-power competition with China and Russia after nearly two decades dominated by deployments in Afghanistan and Iraq. Policymakers are concerned that China will invade Taiwan, pulling Washington into direct conflict with Beijing, while also watching increasing ties between Beijing and Moscow. Meanwhile, war rages on the borders of the North Atlantic Treaty Organization (NATO). The United States and other NATO members have provided the Ukrainian government with hundreds of billions of dollars in financial, humanitarian, and military aid to help defend itself against Russia’s incursion. At the same time, NATO members are themselves involved in intensifying debates over ramping up defense spending in response to the Ukraine invasion; this year, a record eighteen of the alliance’s thirty-two members are due to meet a commitment to spend 2 percent of gross domestic product (GDP) on defense.

The United States and its allies are also wary of Russian President Vladimir Putin’s nuclear saber-rattling, which has stoked concerns over the potential use of nuclear weapons in Europe, as well as Russia’s developments in the space industry. And in the Middle East, there is growing alarm among U.S. officials that the Israel-Hamas war could broaden into a wider regional conflict that could imperil U.S. military forces.