Asymmetric warfare (or asymmetric engagement) is a type of war between belligerents whose relative military power, strategy or tactics differ significantly. This is typically a war between a standing, professional army and an insurgency or resistance movement militias who often have status of unlawful combatants. Asymmetric warfare can describe a conflict in which belligerents' resources are uneven, consequently they both may attempt to exploit each other's characteristic weaknesses. Such struggles often involve unconventional warfare, with the weaker side attempting to use strategy to offset deficiencies in the quantity or quality of their forces and equipment. Such strategies may not necessarily be militarized. This is in contrast to symmetric warfare, where two powers have comparable military power, resources, and rely on similar tactics. Asymmetric warfare is a form of irregular warfare – conflicts in which enemy combatants are not regular military forces of nation-states. The term is frequently used to describe what is also called guerrilla warfare, insurgency, counterinsurgency, rebellion, terrorism, and counter-terrorism. Definition and differences The popularity of the term dates from Andrew J. R. Mack's 1975 article "Why Big Nations Lose Small Wars" in World Politics, in which "asymmetric" referred simply to a significant disparity in power between opposing actors in a conflict. "Power", in this sense, is broadly understood to mean material power, such as a large army, sophisticated weapons, an advanced economy, and so on. Mack's analysis was largely ignored in its day, but the end of the Cold War sparked renewed interest among academics. By the late 1990s, new research building on Mack's insights was beginning to mature, and after 2004, the U.S. military began once again seriously to consider the problems associated with asymmetric warfare. Discussion since 2004 has been complicated by the tendency of academic and military communities to use the term in different ways, and by its close association with guerrilla warfare, insurgency, terrorism, counterinsurgency, and counter-terrorism. Military authors tend to use the term "asymmetric" to refer to the indirect nature of the strategies many weak actors adopt, or even to the nature of the adversary itself (e.g., "asymmetric adversaries can be expected to ...") rather than to the correlation of forces. Academic authors tend to focus on explaining two puzzles in asymmetric conflict. First, if "power" determines victory in conflict, then there must be reasons for why weaker actors decide to fight stronger actors. Key explanations include: Weaker actors may have secret