Guerrilla warfare, warfare waged by irregular forces in generally small-scale operations, often in enemy-held territory. The term (Spanish: “little war”) originally applied to the tactics of Spanish-Portuguese irregulars in the Napoleonic Wars. Traditionally, guerrilla warfare has been waged against larger and better-equipped conventional forces, as in the Viet Cong forces opposing the United States in Vietnam. It is often part of a wider strategy, as for example the activities of the resistance movements in Nazi-occupied Europe, which were part of overall Allied strategy. Guerrilla fighters must avoid open battle as much as possible, exploiting the mobility gained from lack of equipment and supply lines, and making use of popular support. They must rely on hit-and-run tactics, ambush, sabotage, and the psychological effects of unpredictable attack.
Recent years have seen the development of the “urban guerrilla,” whose desire is not to expel an invader by a general insurrection but to so disorganize the fabric of society that a faction can seize power without relying on popular support. To this end, ambush, hijacking, and bombing, directed both at specific targets and at the populace at large, have become increasingly common. With the advent of the nuclear age, guerrilla warfare is perceived to have distinct advantages. It avoids large-scale confrontations that might lead to escalation, is less expensive for aggressors than all-out war, and can be easier to disclaim.