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Note that at Gettysburg, where Lee was on offense, southern casualties were higher.
At, say, Cold Harbor, where Grant was on offense, northern casualties were much higher.
For the Appomattox campaign, the chart shows 10,780 casualties for Grant; none for Lee. That’s obviously incorrect. Lee’s army suffered numbers of casualties from the time when the Petersburg defenses were evacuated to the surrender at Appomattox.