What is the number of soldiers in the Civil War?

Nobody can say exactly. What numbers are available are the total of enlistments for the north. But some men enlisted for two years, some for three, at the start of the war. When that term was up, many reenlisted to see the thing through. Others enlisted in the Union Army over and over again, to collect the money bounty paid to volunteers. Once they were paid, they deserted, and went somewhere else and repeated the process. These were called "bounty jumpers".

The best estimate is that about 2.1 million men served in the Union Armies.

Records were poorly kept in the south, and were often destroyed or lost where they were kept. Estimates range from a low of 600,000 to a high of 1.1 million in the Rebel Armies, with most agreeing that around 900,000 men probably served the Confederacy.