Good point, and we should remember, black soldiers weren’t allowed to serve until the second half of 1862, and it started slowly. By the end of the conflict, 179,000 were in the Union army, many if not most never serving in combat, but performing essential duties that previously had been solely filled by white soldiers; after the war a number of black veterans (and eventually, some new enlistments) were assigned to western forts with a number of those winding up in cavalry units.
A freakish handful of black soldiers served (or well after the war, purported to have served) for some of the CSA states’ forces.
Which was nearly 10% of the Union Army.
Add to those at least 10,000 (16%) serving in the Union Navy.
The death rate from all causes among the Union's two million troops was about 15%.
Among its colored troops deaths were just over 20%.
Colored troops did fight some notable battles, and 18 won the Medal of Honor.
SunkenCiv: "...black soldiers served (or well after the war, purported to have served) for some of the CSA states’ forces."
Well, many tens of thousands of slaves also served the Confederate Army, in a wide variety of infrastructure roles, from building roads & fortifications to miners, teamsters, nurses aids, setting up & maintaining camps, etc., etc.
Civil War historian Allen Guelzo estimates that Lee's Army at Gettysburg, in addition to 75,000 Confederate soldiers included another 30,000 slaves.
Yes, there are scattered reports of slaves serving in combat, but all suggestions for making slaves into Confederate fighting soldiers were squelched until the final days of the war.
No black units ever fought for the Confederacy.