This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book seeks to cut away some of the mythology about Russian hybrid war, using both Western and Russian sources to explore the actual nature of the challenge. It examines how Russia at once fears and seeks to use non-military forms of coercion. The book explores how the notion of hybrid war took root in Western thinking and contrasts that with Russian thinking and practice. It looks at Russian notions of warfighting – which are much more conventionally military than some seem to believe – and how political war emerged, is conceived and organised. The book discusses the particular assets the Russians can deploy in their pursuit of operations short of all-out warfare, from the Special Forces and thuggish gangster auxiliaries who seized Crimea in 2014 to spies, propagandists and spinmasters.