Every war in all history has a different character that defines it. Much of that character is defined by the war fighters themselves. The morale, commitment, and ideology of the soldiers in a conflict dictate the course of the war.
The Civil War was the first war in American history that saw a military draft. Conscription, being the forced military service of all men fitting the qualifications, was prevalent in the Civil War because it was such a contentious conflict. Both the Union and Confederacy had conscription laws that forced tens of thousands of young men into the fight. The introduction of the drafts caused many people to lash out against their governments. It caused problems even within the respective armies as conscripts were perceived as unreliable and disloyal. Desertion was common, and executions were also common as a result. There were however loopholes, clauses, and exemptions that allowed some to avert service. Dodging the draft in any of these ways was looked down on and caused resentment from the men and families who could not avoid conscription.
Conscription is important to an art piece like the Night Before the Battle because it casts light on the mindset of the troops. Any soldier in a such a situation faced with death will naturally question the reason for their mortal danger. Many such soldiers would find the answer was that they were forced against their will on pain of death to fight a battle their had no personal stake in. Something so overbearing is critical to a fighting man, and to the artist trying to capture that fighting man’s struggle.