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 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.