Page "Corps" Paragraph 14

The first corps in the United States Army were legalized during the American Civil War by an Act of Congress on July 17, 1862, but Major General George B. McClellan designated six corps organizations within his Army of the Potomac that spring.

Prior to this time, groupings of divisions were known by other names, such as " wings " and " grand divisions ".

The terminology " Army Corps " was often used.

These organizations were much smaller than their modern counterparts.

They were usually commanded by a major general, were composed of two to six divisions, although predominantly three, and typically included from 10, 000 to 15, 000 men.

Although designated with numbers that are sometimes the same as modern U. S. Army corps, there is no direct lineage between the 43 U. S. corps of the Civil War and those with similar names in the 20th century due to Congressional legislation caused by the outcry from Grand Army of the Republic veterans during the Spanish – American War.

In the Confederate States Army, corps were authorized in November 1862.

They were commanded by lieutenant generals and were usually larger than their Union Army counterparts because their divisions contained more brigades, each of which could contain more regiments.

All of the Confederate corps at the Battle of Gettysburg, for instance, exceeded 20, 000 men.

However, for both armies, unit sizes varied dramatically with attrition throughout the war.

In Civil War usages, by both sides, it was common to write out the number, thus " Twenty-first Army Corps ", a practice that is usually ignored in modern histories of the war.