Infantry units fought in line-of-battle, a two-rank formation that put the enlisted ranks standing shoulder-to-shoulder. Each rear rank man stood one forearm’s length from his front rank file partner, and during combat, he fired over his right shoulder. The purpose of this formation was to mass any given unit’s firepower. With two ranks, the entire line could fire simultaneously, concentrating their efforts on isolated targets. Single, well-aimed volleys, many supposed, would carry the day. However, when combat occurred and battles became prolonged, most units opted to “fire at will,” allowing each infantryman to load and fire at his own pace.
Infantry regiments typically consisted of 10 companies, and each company, by regulation, consisted of three officers, five sergeants, eight corporals, two musicians and about 80 privates. However, under campaign conditions, due to attrition, most companies fielded only 20 to 30 aggregate.
Company commanders usually held a position in the front rank at the extreme right of the company, while regimental staff officers watched from the rear of the regiment. Generals and their staffs and those forming the higher echelons of command—brigade, division, corps, army—monitored the battle from the rear. On several occasions, to inspire the men, they took positions a few paces to the front of the center of advancing line-of-battle.
A thin line of file closers—sergeants and lieutenants—protected the rear, just behind the rear rank. During battle, file closers preserved order and prevented men from deserting.
More on Infantry Units:
Infantry units fought in line-of-battle offensively and defensively. Defensively, a line-of-battle could prove impenetrable. Although sometimes difficult to control under combat conditions because of the thick, white smoke produced by black powder weapons, a defensive line-of-battle produced a massive amount of accurate firepower. A full-strength regiment of 1,000 men, firing at full speed—one round every 20 seconds—could conceivably fire 40,000 ounces of lead in as short a time as 14 minutes. Civil War infantrymen rarely fired so quickly, and during some engagements, depending upon terrain, weather or if the unit was resupplied, defensive combat could last several hours. In any case, the accuracy of rifled muskets—the primary weapon of most infantrymen—produced a deadly field of fire in front of defensive line-of-battle.
Offensively, infantry lines-of-battle became more vulnerable, as they could not easily load and fire while on the move. Offensive lines-of-battle used bayonets to drive enemy units from key positions, but time and again, they suffered heavy casualties—or even defeat—for their attempt. Shoulder-to-shoulder formations provided inviting targets for enemy artillery and infantry, and throughout the war, advances over open ground produced high casualty rates. However, linear formations proved entirely necessary for officers to preserve command and control.
Additional Fighting Formations
Infantry units fought in a number of other linear formations. Infantry units formed in skirmish lines, consisting of a single rank of men, each five or more paces apart, when making contact with the enemy or when protecting the front or flank of certain defensive positions. These lines could move through rugged terrain more easily than could a line-of-battle, and they could cover ground more quickly, delaying advancing enemy lines-of-battle.
Later in the war, commanders developed more effective offensive formations, including the “close column by division.” Here, regiments formed into a narrow column, two companies wide and 10 ranks deep. This formation presented a slender front, allowing regiments to pass over ground quickly, sustain fewer casualties and preserve the morale and physical shock of their attack. Close column by division formations and similar adaptations worked exceedingly well at several battles—Spotsylvania, Cold Harbor, Fort Harrison and the final assaults at Petersburg—puncturing an entrenched enemy position with impunity. However, at other battles, most notably at Kennesaw Mountain, where steep or rugged terrain did not favor a dense formation, attack columns stalled, forcing the soldiers to pile up and incur heavy casualties.