Concern about the potential for military interventions by U.S. adversaries to affect U.S. interests has risen over the past decade, driven by high-profile interventions, such as the Russian missions in Ukraine and Syria, Iranian activity in Iraq and Syria, and expanding Chinese military activity in Africa. Despite these concerns, relatively little is known about the intervention behavior of these countries. There are many reasons for U.S.

policymakers to be concerned about the interventions of adversaries. First, adversary interventions might pursue outcomes that undermine U.S. interests. Second, adversary interventions might affect the activities and objectives of U.S. forces when they intervene in the same places. Finally, adversary interventions may directly threaten U.

S. forces or U.S. allies. In this report, the authors explore where, how, and how often U.S. adversaries (specifically, Russia, China, and Iran) have intervened militarily since 1946 and identify why these adversaries have initiated military interventions and why they might do so in the future. Three companion reports consider Chinese, Russian, and Iranian military intervention behavior.

The insights and signposts identified can inform U.S. decisions about military posture, partnerships, and investments.