In the decades since the fall of the Berlin Wall there has been a substantial amount of strategic thinking about irregular war. Broadly defined by what it is not – irregular war is not conventional or regular war between two organized militaries of opposing states – this form of war includes at least one non-state entity. Terrorism, insurgency and guerrilla warfare may be considered as part of irregular war. Guerrilla warfare refers to the tactics of hit and run, of enemies who avoid direct battles by hiding in the countryside or urban areas, of opponents who, in the words of C.E. Callwell at the turn of the twentieth century, refuse ‘to meet [regular forces] in the open field’.1 Terrorism eludes a commonly accepted definition, but generally includes attacks on civilians or non-combatants, the seemingly random use of violence and the purposeful creation of fear or panic to intimidate a population or compel a government to do or not do something. Like guerrilla war, terrorism, notes contemporary strategic thinker David Kilcullen, ‘is in the tactical repertoire of virtually every insurgency’.2