P.W. Singer and Emerson Brooking argue that social media has become a theater of warfare where battles for narrative shape political outcomes as surely as military operations. Drawing on their defense policy expertise and years of research, they trace how ISIS weaponized social media using tactics borrowed from Taylor Swift and influencer culture, how Russian information operations exploit platform dynamics, and how domestic actors have learned the same techniques. The book provides case studies ranging from terrorist recruitment to election interference, examining the specific mechanisms by which content goes viral and how adversaries exploit these mechanisms. Singer, a strategist who has advised multiple administrations, and Brooking, a former policy analyst, combine technical understanding of platforms with geopolitical analysis. They interview military commanders, social media executives, and the trolls themselves to construct a comprehensive picture of this new battlespace. The book examines how the attention economy creates incentives for extremism, why outrage spreads faster than truth, and how authoritarian states have learned to use platforms designed for openness. Readers seeking to understand how their information environment became so contested and what forces shape their social media feeds will find both explanation and alarm. Singer and Brooking document a transformation in how power operates, with implications for national security, democracy, and the experience of being online.