American Civil War Regimental Formations and Movements

Overview

The American Civil War saw a transition from Napoleonic linear tactics to more dispersed, modern engagements. This transition was largely driven by the replacement of the smoothbore musket with the rifled musket, which extended the effective kill zone from 100 yards to 500+ yards.

Key Drill Manuals

1. Winfield Scott's Infantry Tactics (1835): Emphasized close-order formations (elbow-to-elbow) to maintain alignment and mass fire. It remained highly influential early in the war but failed to account for the increased range of rifled muskets.
2. William J. Hardee's Rifle and Light Infantry Tactics (1855): Based on the French Chasseurs à Pied doctrine, it emphasized increased rates of march ("double quick") to cross the expanded rifle kill zone quickly, and expanded skirmishing drill.
3. Silas Casey's Infantry Tactics (1862): A three-volume Union update that incorporated Jomini's principles and expanded brigade-level evolutions, formalizing the assignment of specific light/skirmish companies.

Primary Formations

Based on Antoine Henri Jomini's Summary of the Art of War, there were five fundamental ways to deploy troops:

• Line (Line of Battle): The predominant battlefield formation for both attack and defense. A regiment formed two ranks deep, 13 inches between ranks, with files lightly touching elbows. It allowed maximum firepower but was difficult to maneuver in rough terrain.
• Column: Used primarily for maneuver, approach, and massing troops.
• March Column: Typically a column of fours (four abreast) used for rapid road movement (prescribed speed of 2 mph).
• Attack / Field Column: Formed by companies or divisions (two companies). Provided greater mobility and shock value against a narrow front but presented a dense target vulnerable to artillery and rifled fire.
• Skirmish Order: A loose, open formation deployed 300 to 500 yards ahead of the main line. Skirmishers operated in four-man groups separated by 20 to 40 paces. Initially consisting of 1-2 companies per regiment, by late war, entire regiments or brigades deployed in open order to probe defenses and absorb initial fire.
• Square: A dense, hollow or solid formation facing outward, designed to repel cavalry. Heavily drilled but rarely employed in the ACW, as rifled musketry devastated cavalry charges long before they could reach infantry squares.
• Deep Masses / Wave Attacks: Successive lines stacked behind one another (e.g., Spotsylvania Court House). Intended to provide continuous momentum, but lines frequently bunched up into giant, chaotic columns under fire.

Movements and Maneuvers

• Advance / Withdraw: Direct forward or backward movement in line of battle.
• By the Flank: A regiment moving sideways (left or right). The movement rate was halved, and the unit marched in a narrow profile.
• Wheel: A change of direction where one flank pivots while the rest of the line swings forward or backward to conform to the new facing, moving like the spoke of a wheel.
• Oblique: The unit moves diagonally (up to 45 degrees) while all men maintain their original facing. Used to shift the line laterally while advancing or withdrawing.
• Refuse the Flank: A defensive maneuver where the stands on a regiment's flank swing backward (up to 45 degrees) to prevent the enemy from turning or enfilading the line.
• About Face: The entire unit turns to face the opposite direction, allowing rapid reversal of movement without complex reforming.
• Deployment / Doubling: The complex mechanics of expanding from a march column of fours into a two-rank battle line, or condensing back into column.

[!NOTE] By 1864, the high casualties inflicted by rifled musketry on close-order formations forced the widespread adoption of entrenchments, rifle pits, and looser skirmish-style advances, rendering many of these formal maneuvers obsolete.