Part 5 gives researchers an inside look at army organization, strategic and tactical planning, support, and prosecution of "the first modern war." Materials in the collection provide insights into officers' thinking, their relations with one another, efforts to secure promotions, and motivations behind their planning and conduct of operations. The materials in Part 5 are organized in four categories: Armed Forces, Federal Troops, Named Units, and U.S. Naval Forces.
Part 5 brings together general histories and personal narratives of the artillery, the cavalry, communications, espionage, the quartermaster/commissary of subsistence, transportation, and medical
service. A notable strength of Part 5 is its detailed data on the medical services and sanitary conditions endured by the armed forces. Statistical and graphical data, medical reports, and direct observations explain why death from disease was twice as common as death from combat wounds. The history of the U.S. Cavalry can be studied using Albert G. Brackett's classic work and other materials in the collection. Scholars can trace the transition in communications, fostered by Secretary of War Stanton, from the Signal Corps' visual signals to the U.S. Military Telegraph Services' electrical signals.
The story of Union espionage-from Allan Pinkerton's largely unsuccessful secret service bureau to the "bullyboy" methods of the War Department's Lafayette C. Baker-is also revealed in these materials. Items on the Quartermaster Department and the Commissary of Subsistence Department provide in-depth information on the development, administration, and organization of both departments. The use of railroads to transport troops and supplies made a critical contribution to the Union
victory. The recollections of Herman Haupt, chief construction engineer of the U.S. Military Railroad, have unique importance, since official records are meager.