Russia's conventional capabilities pose a serious threat to NATO that remains mostly untested. Where it has historically succeeded is in using various types of hostile measures to sow disorder, weaken democratic institutions, and undermine NATO cohesion and what Russia perceives as the eastward expansion of Western institutions. However, Russia also has a long track record of strategic shortfalls, and even some ineptitude. Formulating strategies for addressing these actions demands a clear understanding of how and why Russian leaders employ hostile measures-for example, economic embargoes, limited military incursions, cyberattacks, and information campaigns. A historical review of Soviet-era power dynamics and detailed case studies of Russian hostile measures in the post-Soviet era help clarify the conditions under which Russia employs hostile measures and the vulnerabilities it exploits in the countries it targets-as well as the messages these measures send to other key audiences, such as Russia's domestic public, the Russian diaspora, and Western powers that Russia perceives as encroaching on its sphere of influence. NATO and other Western powers will benefit from exploring opportunities to deter, prevent, and counter Russian hostile behavior in the so-called gray zone short of war, where daily adversarial competition occurs. Many of the behaviors that Russia exhibits in the gray zone will no doubt extend to conventional war.