The deterrence of armed conflict has been studied intensively for decades, as have escalation dynamics along the path to such conflicts. The deterrence of forms of aggression below the level of armed conflict—such hostile measures as economic coercion, political subversion, and military intimidation—has received much less attention. Such forms of strategic competition, however, lie at the heart of the United States’ current National Defense Strategy.

In this report, we seek to understand how the United States might use its military posture in Europe—particularly focusing on ground forces—as part of a strategy to deter Russian malign activities in the competition space. At a broad level, we seek to understand: • Under what conditions has U.S. forward military posture historically deterred competitors from undertaking hostile measures below the level of armed conflict?

• When has the U.S. forward military posture provoked competitors to undertake even greater hostile measures?

• When changes in U.S. forward military posture have provoked competitors, what forms have their hostile measures taken?

More narrowly, we explore how these dynamics should inform U.S. posture decisions for Europe, asking: • How might the United States’ forward military posture be used to deter Russia from additional aggressive actions in the competition space?

• What U.S. military posture might provoke Russia to escalate?

• What are Russia’s escalation options and their implications?

• What preventive or mitigating measures can the United States take to reduce the likelihood of escalation?