Townsend draws on battle reports not found in the Official Records, on personal papers, and on other nonpublished material to examine Osterhaus’s part in the major battles in the West as well as in minor engagements. She tells how he came into his own in the Vicksburg campaign and proved himself through skill with artillery, expertise in intelligence gathering, and taking the lead in hostile territory—blazing the trail down the west side of the river for the entire Union army and then covering Grant’s back for a month during the siege. At Chattanooga, Osterhaus helped Joe Hooker strategize the rout at Lookout Mountain; at Atlanta, he led the Fifteenth Corps, the largest of the four corps making Sherman's March to the Sea. Townsend also documents his contributions in the battles of Wilson's Creek, Pea Ridge, Arkansas Post, Port Gibson, Ringgold Gap, and Resaca and shows that he played a crucial role in Canby’s Mobile Bay operations at the end of the war.