In a general sense, armies fought with a certain set of tactical assumptions:
- Civil War soldiers believed in the importance of linear tactics. They believed any line of troops must be contiguous and supported by reserves in the rear.
- They believed that the flanks of an army needed to be secured by abutting them against impassible terrain features, refusing them (pulling them back) or protecting them with skirmishers to warn of an attack from that direction.
- Most generals believed armies needed to use “combined arms,” that is, a concerted action of the infantry, artillery and cavalry branches, to secure pivotal positions.
- They believed that enemy defensive positions, while dangerous, could be carried by assault, and must be carried, if victory was to be achieved.
By late 1863, a fifth assumption emerged that when not actively engaged, armies must entrench and fortify their positions with elaborate breastworks. During the war’s later months, armies constructed elaborate fortifications: log works, earthen redoubts, redans and fortresses, complete with palisade and abatis—felled logs and trees—to deter attackers.
Entrenchments prevailed among the war’s last campaigns—the Mine Run Campaign, the Overland Campaign, the Petersburg Campaign, the Atlanta Campaign, and the Nashville Campaign—and these changes made frontal attacks increasingly risky. Nevertheless, direct attacks persisted, and while many led to disaster, others brought about the key successes that led to Union victory.
Historians disagree on the significance of linear tactics, calling them alternately foolish or brilliant. In any event, those who orchestrated them or participated in them generally believed that linear tactics produced the conditions needed for victory. Not until after the conflict did military professionals analyze their application or openly question their use.