Attrition warfare is a strategic concept that to win a war, one's enemy must be worn down to the point of collapse by continuous losses in personnel and materiel. The war will eventually be won by the side with greater such reserves.

A well known example of this is during World War I on the western front where both forces found themselves in static defensive positions in trenches that ran from the Swiss Alps to the English Channel. For years without any opportunity for maneuvers, the only way the commanders thought they could defeat the enemy was to continually attack each other head on and to grind the other down.

The Vietnam War has frequently been called a war of attrition, the American strategy being to wear down the enemy until he lost his "will to fight". Ultimately, this strategy would prove unsuccessful, perhaps due to the asymmetrical nature of the conflict and the profound underestimation on account of the United States of the determination of North Vietnam.

If the sides are evenly matched or nearly so, the outcome of a War of Attrition may be a Pyrrhic victory.

See also:

• Battle of attrition
• Fabian Strategy
• Maneuver warfare