Since Vladimir Putin’s inauguration as Russia’s president following the tumultuous tenure of Boris Yeltsin, Russia has implemented a coordinated policy of conventional espionage measures, cyber intrusions, and information operations targeting the United States. Validated on the multi-domain battlefields and computer networks of vulnerable Baltic neighbors, Russia’s active campaigns of intelligence and influence operations have caught the United States off-guard. Four successive U.S. presidential administrations have grappled with Russian aggression, but U.S. responses have consistently lacked cohesion, strategy and effectiveness in deterrence. Russia’s weaponization of social media and willingness to attack the foundations of American democracy have made the development of a coherent U.S. strategy a matter of urgent national importance. By examining the underlying doctrine of hybrid warfare, the specific tactics that Putin’s Russia is using against the United States and highlighting recent U.S. responses to Russian espionage and cyber influence campaigns, this paper identifies the potent tools and patterns of hybrid warfare strategy that collectively constitute a growing threat to U.S. national security. While hybrid warfare falls short of conventional military conflict in the metric of physical destruction, its deleterious effects on American security are undeniable and suggest the need for a long-term, comprehensive strategy from the United States.