Sons of Yamato: IJA
The Imperial Japanese Army of 1939-1942 was an army at the height of their conquests. The professional army was full of highly motivated veteran troops from the years of fighting against the Chinese and their conquests of Manchuria.
The seemingly invincible army suffered its first major blow against the Soviet forces at Nomonhan, but would recover from the defeat to execute a rapid conquest of the Southeast Asia.
Sundered Union: Army of the Potomac
At the start of the American Civil War, the United States had a small standing army. The states provided regiments and eventually these regiments would be organized into army groups. In the Eastern Theater, the Army of the Potomac was the principal Union force and underwent multiple commanders.
The Army of the Potomac was the force that fought and won against General Lee's Army of the Northern Virginia at Gettysburg.
Sundered Union: Army of Northern Virginia
The Army of Northern Virginia began as the Army of the Potomac (CSA) and evolved into the legendary Army of Northern Virginia under General Robert E Lee.
The primary force for the Confederates in the Eastern Theater, the army was involved in most major battles in the theater until its surrender at Appomattox Courthouse.