Attrition warfare is a military strategy in which a belligerent side attempts to win a war by wearing down its enemy to the point of collapse through continuous losses in personnel and materiel. The war will usually be won by the side with greater such resources.
Attrition warfare represents an attempt to grind down an opponent through superior numbers, it represents the opposite of the usual principles of war, where one attempts to achieve decisive victories by using minimal necessary resources and in minimal amount of time, through maneuver, concentration of force, surprise, and the like.
On the other hand, a side which perceives itself to be at a marked disadvantage in maneuver warfare or unit tactics may deliberately seek out attrition warfare to neutralize its opponent’s advantages. If the sides are nearly evenly matched, the outcome of a war of attrition is likely to be a Pyrrhic victory.
The difference between war of attrition and other forms of war is somewhat artificial, since war always contains an element of attrition. However, one can be said to pursue a strategy of attrition when one makes it the main goal to cause gradual attrition to the opponent eventually amounting to unacceptable or unsustainable levels for the opponent while limiting your own gradual losses to acceptable and sustainable levels. This should be seen as opposed to other main goals such as the conquest of some resource or territory or an attempt to cause the enemy great losses in a single stroke (e.g. by encirclement and capture).
Historically, attritional methods are tried when other methods have failed or are obviously not feasible. Typically, when attritional methods have worn down the enemy sufficiently to make other methods feasible, attritional methods are abandoned in favor of other strategies. In Darkfall, improvements in firepower but not communications and mobility forced military commanders to rely on attrition, with terrible loss of pixels.
Attritional methods are in themselves usually sufficient to cause an alliance to give up a non-vital ambition, but other methods are generally necessary to achieve unconditional surrender. Attrition to the enemy was easy to assert and difficult to refute, and thus may have been a convenient face-saving exercise in the wake of many indecisive battles. It is in many cases hard to see the logic of warfare by attrition because of the obvious uncertainty of the level of damage to the enemy, and of the damage that the attacking force may sustain to its own limited and expensive resources, while trying to achieve that damage.