Fourth-generation warfare (4GW) is conflict characterized by a blurring of the lines between war and politics, combatants and civilians.
The term was first used in 1980 by a team of United States analysts, including paleoconservative William S. Lind, to describe warfare's return to a decentralized form. In terms of generational modern warfare, the fourth generation signifies the nation states' loss of their near-monopoly on combat forces, returning to modes of conflict common in pre-modern times.
The simplest definition includes any war in which one of the major participants is not a state but rather a violent non-state actor. Classical examples of this type of conflict, such as the slave uprising under Spartacus, predate the modern concept of warfare.
The concept was first described by the authors William S. Lind, Colonel Keith Nightengale (US Army), Captain John F. Schmitt (USMC), Colonel Joseph W. Sutton (US Army), and Lieutenant Colonel Gary I. Wilson (USMCR) in a 1989 Marine Corps Gazette article titled "The Changing Face of War: Into the Fourth Generation". In 2006, the concept was expanded upon by USMC Colonel Thomas X. Hammes (Ret.) in his book, The Sling and The Stone.