Despite the supposed taboo against the practice, many governments, rebels, and terrorist groups use children in war to spy and kill. In Tools of War, Tools of State, Robert Tynes examines this complex problem, demonstrating that the modern use of children in war is a tactical innovation. He discusses how boys and girls on the battlefield bolster troop size, create moral dilemmas, and deepen the level of fear. He also reveals how the practice has become an essential component for groups such as ISIS and al-Shabaab, in their state-making projects. Using statistical methods to analyze conflicts from 1987 to 2007, Tynes shows how widespread child soldier use is and confirms the theory that it is tactically advantageous. Through historical analysis, he explains how child soldiering developed out of Mao's protracted war theory and the militarization of youth during the twentieth century. A case study of the civil war in Sierra Leone, which details the brutality involved when children are forced to fight, is included.