To make attrition work in his favor, a military leader must be able to force his enemy to fight, as Grant could force Lee to fight when he had Lee locked into a defense of the Confederate capital of Richmond in the last year of the Civil War and as the American and British armies could make Hitler’s Wehrmacht do after the landing at Normandy in 1944. … Thayer’s findings proved that Westmoreland was unable to force his enemy to fight, because the Vietnamese had an overwhelming grasp of the initiative.

Neil Sheehan, A Bright Shining Lie, loc. 1991