Why did Ulysses S. Grant use a strategy of attrition against Robert E. Lee's army?

Ulysses S. Grant adopted a strategy of attrition against Robert E. Lee’s Army of Northern Virginia because he recognized that the Union possessed a significant advantage in manpower and industrial resources, whereas the Confederacy had a much smaller population and limited capacity to replace its losses.123

During the 1864 Overland Campaign, Grant realized that while both sides suffered heavy casualties, the losses were proportionally more devastating to Lee’s smaller force. By engaging in continuous, aggressive combat, Grant aimed to sap the Confederate army's strength and its willingness to fight. Even in battles that were tactically inconclusive or resulted in high Union casualties, such as the Battle of the Wilderness and the Battle of Spotsylvania Court House, the strategy succeeded in reducing the Confederate numbers.14

Ultimately, Grant leveraged the Union's superior resources to force Lee into a war of attrition that the South could not sustain, leading to the Petersburg Campaign and the eventual collapse of Confederate resistance.51