According to widespread belief in the United States and Europe, Vladimir Putin’s Russia has unleashed “hybrid war” against the West. The concept covers all forms of assault short of war itself: cyberattacks, targeted propaganda, “little green men” (Russian “volunteers” appearing in Ukraine without insignia), aid to fringe opposition parties, and military threats. In this disciplined study, Fridman does not deny that Russia does all these things, but he is more interested in scraping away the misunderstandings surrounding the concept itself. He explains where the notion of hybrid war comes from, how Americans and Russians understand it differently, and, above all, why and how it has been deployed and politicized in the war in Ukraine. The idea of combining military force with other resources to sap an opponent’s will to fight is as old as war itself. But the modern concept of war fought by multiple means, on and off the battlefield, originated with the U.S. military over the course of several wars. The current, more expansive Russian version reflects what its Russian authors believe were the West’s own methods of waging the Cold War, which they now see being used against Russia once again.