Military theorists and strategists have viewed attrition warfare as something to be avoided. In the sense that attrition warfare represents an attempt to grind down an opponent through superior numbers, it represents the opposite of the usual principles of war in which one attempts to achieve decisive victories by using minimal necessary resources and in minimal amount of time, through manoeuvre, concentration of force, surprise, and the like.
On the other hand, a side that perceives itself to be at a marked disadvantage in manoeuvre 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. One can be said to pursue a strategy of attrition if 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 one's own gradual losses to acceptable and sustainable levels. That 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 (such as by encirclement and capture).
Historically, attritional methods are tried only as a last resort, 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 World War I, improvements in firepower but not communications and mobility forced military commanders to rely on attrition, with terrible casualties.
Attritional methods are in themselves usually sufficient to cause a nation to give up a nonvital ambition, but other methods are generally necessary to achieve unconditional surrender.