News of the invasion prompted many who were nearly recuperated in hospitals, North and South, to hasten toward the front and rejoin their units. Some made it back in time to participate in the battle.
As the armies passed through Maryland, a few volunteers joined the Union army, while perhaps a few dozen joined the Confederate army. It is supposed, however, that a majority of these raw recruits proved to be more of a hindrance than a help, and the arduous physical demands of soldier life soon dampened their initial enthusiasm. That was similarly true of hastily raised militia commands, which prompted much mirth among hardened veterans, see also:
Federal militia forces raised in response to the Confederate invasion were impressive enough on paper, and might have been effectively employed cutting Lee’s line of communications back to Virginia, but evidently they did not pose much of a direct challenge to Lee’s veterans. John B. Gordon’s...
civilwartalk.com
A couple more examples:
"While we were at Funkstown [July 11] large reinforcements came up, mostly nine-months men. One of these regiments was put into our brigade, but day before yesterday's [July 15] march used them up completely. When we stopped for dinner only twenty-five men were left, officers and colors being back on the road. Their time was out that night and they did not come further with us, and have gone home before this I suppose." (July 17 letter of 1st Sergeant Joseph P. Burrage, Company H, 33rd Massachusetts, Center for Applied Technologies in the Humanities, Virginia Tech)
At Frederick City … there was some militia there, hastily called out and badly armed – some of them with shotguns. The Seventh Regiment National Guard of New York City was also there for another thirty days' war experience, and was guarding Government stores at the railroad depot. They looked very jaunty in their neat and unsoiled uniforms, some of them wearing paper collars, forming a striking contrast to the bronzed and begrimed veterans of the Army of the Potomac, from whom the Seventh had to endure much good-natured chaffing in passing. (Ten Years in the Ranks, U.S. Army, by Augustus Meyers – 2nd U.S. Infantry, Brigade Commissary – NY: The Stirling Press, 1914)
Bringing the