Attrition was Grant's strategy, not his tactics, tactically he wanted to maneuver to best use the effects of attrition arising from maneuver, but he more often failed to maneuver to advantage and ended up performing assaults on fortified positions.
Strategy is doing the right job, tactics is doing the job right.
To quote his own words:
I determined, first, to use the greatest number of troops practicable against the armed force of the enemy, preventing him from using the same force at different seasons against first one and then an- other of our armies, and the possibility of repose for refitting and producing necessary supplies for carrying on resistance. Second, to hammer con- tinuously against the armed force of the enemy and his resources, until by mere attrition, if in no other wav, there should be nothing left to him.
How to measure his performance and what does it then support? One way is to use cost benefit, ie if 1 man makes 1 car a day and in another factory it takes 2 men to make the same car, then the first factory is twice effective. Using casualty infliction and casualties sufferers to inflict them, is a way to measure a the cost benefit of attrition strategy.
Grant's overland cost effective at inflicting combat losses and suffering them. If you add up the strength of both sides, and do a cost benefit calculation, Lee with 344,000 manpower, fought Grant's 634,000 manpower, so Grant's manpower advantage was 1.8 to 1. Lee inflicted 97,000 casualties and suffered 62,000 to do so, coming out at +28% and minus 18% to Grants, +10% -15%. Or, in other words, Grant's 1.8 manpower advantage returned a casualty infliction rate almost three times less than Lee, for around the same loss rate in doing so. or if you prefer , Lee inflicted three times the loss rate that Grant achieved, for the same loss rate each suffered. Hence he is called a butcher, he was losing manpower at a rate close to the North's military age manpower advantage, and higher than the manpower advantage the Northern armies contained. Forty-five percent of all Union casualties-including 56.4 percent of all Union troops wounded and 36.4 percent of all Union troops killed in action fell at the hands of Lees army.
So, to remove a casualty required Grant to lose 3 of his own, and vice versa, in that measurement his strategy of attrition skirted with defeat for the North, as it was higher than the North's mobilisation rate.
US to CS PFD manpower advantage.
62 April 1.59 to 1.
62 Dec 2.6 to 1.
63 Dec 1.79 to 1.
64 Dec 2.16 to 1.
He was called a butcher earlier in 62 by a US Senator who wanted Lincoln to sack him, calling him "bloodthirsty, reckless of human life and utterly unfit to lead troops".
"I'll fight it out along these lines if it takes all summer." is a quote that he is not moving back onto supplies and reinforcements, as had been the usual, but that they are coming to where he is going to be. Full quote and its meaning is in S Foote.
Haig is also known as a butcher, he lost 0.3% of his Army a day in 1916. He lost 2.4% of all British casualties of the war on first day of the Somme, something he never repeated. Grant was losing combat casualties at twice the rate of Haig in the campaign, also lost 2.8% of all US casualties at wilderness, and again at Spotsylvania, 2% at Cold Harbour, and another 2% at Shiloh, 1.9% at the 2nd Petersburg assault so repeated the process of mass causalities.
British Army (1.5 million strong) WW1 Somme, 50 of the 58 Division took part during 141 days, so 1,293,100 used, of which 420k became combat casualties, or 32%, or 3k a day casualties or 0.3% of strength a day.
SU Army in WW2 Eastern front, 3rd Quarter of 1941, Army strength average of 3,334,000 per month, so c10,000,000 took part in 90 days, of which 2,744,765 became casualties, or 27.4% or 30,497 a day or 0.9% of strength a day.
Grant's Army in the 40 days Overland, AoP 142,744, reinforcements and replacements, received from Belle plain 33,264. From White house 23,514. Total of c200k not including sick, of which 55,000 became combat casualties or 27.5% or 1375 a day, or 0.7% of the Army lost per day.
646,392/1505 days = 429 or 8.5% of all wartime casualties in 2.7% of the days is Grant's record.