Tough choice, but as no one so far chose the Overland Campaign, I'll give it a vote.
Here is where he was regrettably given the sobriquet "the butcher", for the great number of casualties sacrificed in this campaign.
The facts are that General Grant inherited a large, well trained army. He also inherited an army which, by virtue of its history with its prior commanders, was accustomed to be timid and self protective.
Additionally, in the army he inherited, the most hardened veterans of the AoP were due for mustering out, and who could blame those that did?, and so the ranks were filled with all sorts of also rans, so different from the Army of the Tennessee with which he vanquished most of the South.
Now with this force, and he also took in a lot of Heavy Arty prima donnas, etc., he determined to end the war by defeating the ANV.
We can say the ANV was depleted and had no chance against the numbers of Grant's AoP, but that excuse never stopped them before. The ANV had never before met such a determined adversary.
His achievement was due to the fact that in this long campaign, tho Lee sometimes beat him to the punch, he took and continued to maintain the strategic initiative throughout. He never turned back.
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