 May 12 was the most intensive day of fighting during the battle, with Union casualties of about 9,000, Confederate 8,000; the Confederate loss includes about 3,000 prisoners captured in the Mule Shoe.Despite the significant casualties of May 12, Grant was undeterred.He telegraphed to the Army's chief of staff, Maj. Gen. Henry W. Halleck, "The enemy are obstinate and seemed to have found the last ditch."