The U.S. Army in the years following the Civil War lacked standing organization at the corps and division levels .
It moved swiftly to adopt these during the mobilization for the Spanish -- American War in the spring of 1898 .
Although the U.S. Army in the years following the Civil War lacked standing organization at the corps and division levels , it moved swiftly to adopt these during the mobilization for the Spanish -- American War in the spring of 1898 .