Attrition warfare is a military strategy consisting of belligerent attempts to win a war by wearing down the enemy to the point of collapse through continuous losses in personnel and material. The word attrition comes from the Latin root atterere, meaning "to rub against", similar to the "grinding down" of the opponent's forces in attrition warfare.
Attrition warfare represents an attempt to grind down an opponent's ability to make war by destroying their military resources by any means including guerrilla warfare, people's war, scorched earth and all kind of battles apart from a decisive battle. Attrition warfare does not include all kinds of Blitzkrieg or using concentration of force and a decisive battle to win. The side that reinforces their army at a higher speed will normally win the war. Clausewitz called it the exhaustion of the adversary.
A side that perceives itself to be at a marked disadvantage may deliberately seek out attrition warfare to neutralize its opponent's advantages over time. Sun Tzu has stated, that there is no country that has benefitted from prolonged warfare, but Russia in 1812 won the war with attrition warfare against Napoleon. When attritional methods have worn down the enemy sufficiently to make other methods feasible, attritional methods are often complemented or even abandoned by other strategies. But in World War I military commanders on both sides relied on attrition warfare resulting in terrible casualties without a strategic result.
The difference between war of attrition and other forms of war is somewhat artificial since even a single battle normally 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). Attrition warfare also tries to increase the friction in a war for the opponent.
The French invasion of Russia is a textbook example how elements of attrition warfare interfered with Napoleon's military logistics and won the war without a decisive battle. One of the best visual representations of the Russian attrition warfare strategies was created by Charles Joseph Minard. It shows the steady decrease of the number of soldiers of the French Grande Armée during the course of the war.
The best-known example of attrition warfare might be on the Western Front during World War I. Both military forces found themselves in static defensive positions in trenches running from Switzerland to the English Channel. For years, without any opportunity for maneuvers, the only way the commanders thought that they could defeat the enemy was to repeatedly attack head on and grind the other down.
One of the most enduring examples of attrition warfare on the Western Front is the Battle of Verdun, which took place throughout most of 1916. Erich von Falkenhayn later claimed that his tactics at Verdun were designed not to take the city but rather to destroy the French Army in its defense. Falkenhayn is described as wanting to "bleed France white" and thus the attrition tactics were employed in the battle.
Soldiers on the Italian Front fought a series of battles of attrition along the Isonzo River between June 1915 and November 1917.
Attritional warfare in World War I has been shown by historians such as Hew Strachan to have been used as a post hoc ergo propter hoc excuse for failed offensives. Contemporary sources disagree with Strachan's view on this. While the Christmas Memorandum is a post-war invention, the strategy of attritional warfare was the original strategy for the battle.
An example in which attritional warfare was stumbled into without intent occurred during the latter part of the American Civil War, when Union general Ulysses S. Grant continually attempted to force the Army of Northern Virginia into a decisive engagement in the open, but was prevented from doing so by the quick repositioning and refortification by Robert E. Lee. Due to this, the Army of the Potomac was forced to attempt to dislodge its counterpart with direct attacks against entrenched positions on numerous occasions.
While these did not yield the breakthrough that Grant had hoped for, and the Union casualties were higher by volume as a result, the Union was able to replenish its forces more readily, and the Confederacy began taking a higher percentage of casualties compared to its overall capacity. By the time Grant finally forced Lee into an open engagement at the Battle of Appomattox Court House, the Army of Northern Virginia was unable to mount an effective counterattack against a fraction of the Union army, and subsequently surrendered.