 The two-day battle of Shiloh, the costliest in American history up to that time, resulted in the defeat of the Confederate army and frustration of Johnston's plans to prevent the two Union armies in Tennessee from joining together.Union casualties were 13,047 (1,754 killed, 8,408 wounded, and 2,885 missing); Grant's army bore the brunt of the fighting over the two days, with casualties of 1,513 killed, 6,601 wounded, and 2,830 missing or captured.Confederate casualties were 10,699 (1,728 killed, 8,012 wounded, and 959 missing or captured).