Part two in a series.
In the first part of this series, we learned Napoleon Bonaparte’s theories about the use of cavalry in the field. Those tactics relied on the short range of the long arms of the infantry and the smoothbore artillery.
Prof. Dennis Hart Mahan, who taught military science at the United States Military Academy at West Point, took Napoleon’s teachings, refined them, and then taught them to the cadet corps. Those former cadets ended up as the highest-ranking officers of both sides on the Civil War. Before we get to Mahan’s teachings, we need to get a sense of who Dennis Hart Mahan was.
Mahan was born in New York City on April 2, 1802 and was raised in Norfolk, Virginia. Mahan was appointed to attend West Point from Virginia. While still a cadet, Mahan taught mathematics to his fellow cadets. He graduated first in the class of 1824, and soon returned to West Point to teach civil and military engineering. From 1826 to 1830, he studied public engineering works and military institutions in Europe. When he returned to West Point, he taught engineering as well as the course in military science taken by every cadet before graduation, including every West Pointer who fought in the Civil War. A recognized authority on military engineering, Mahan wrote several books that were considered standards in his field, including Complete Treatise on Field Fortification (1836), Summary on the Cause of Permanent Fortifications and of the Attack and Defense of Permanent Works (1850), and An Elementary Course of Military Engineering (2 vol., 1866–67). More important, Mahan authored Elementary Treatise on Advance-Guard, Out-Post, and Detachment Service of Troops (1847, often reprinted), which was the first comprehensive textbook on tactics and strategy taught to West Point cadets.
Mahan and his wife Mary Helena Okill had five children, including Alfred Thayer Mahan, who became a renowned naval strategist and historian whose work was as influential as his father’s.
Dennis Hart Mahan committed suicide at Stoney Point, New York in September 1871, resulting from his inability to cope with being forced into retirement. Mahan, however, left an indelible thumbprint on American military doctrine. His interpretations and adaptations of Napoleonic theories—and specifically of Jomini’s theories—served as the sole military tactics textbook for West Point cadets. His teachings dominated the early phases of the Civil War.
These are Mahan’s rules for the use of cavalry, as set forth in his Elementary Treatise on Advance-Guard, Out-Post, and Detachment Service of Troops:
19. Position. This arm is usually placed in the rear of the infantry, on ground favorable to its manoeuvres, and where it will be masked from fire until the moment arrives to bring it into action; here, it acting on the defensive, the cavalry watches its opportunity to support the other troops, driving back the enemy, by prompt and vigorous charges, when these are hard pressed; or, if on the offensive, biding its time, to rush upon the assailant, and complete his destruction, when his ranks commence to waver or show signs of disorganization from the assaults of the other arms.
20. Formation. The habitual formation of cavalry for the attack is in a line of two ranks, with a reserve or support to its rear. The supports are indispensably requisite to guard against those chances of danger to which cavalry is particularly exposed, if attacked in turn, when in a state of partial disorganization, after a successful charge, or when threatened by an offensive movement against its flanks. The supports offer a safeguard against either of these dangers; for, if the front line is brought up by the enemy, after a successful charge, it can retire and rally in the rear of the supports; and if the enemy makes a movement against the flanks, the supports placed behind them and in column, can form and anticipate the enemy’s charge. For the foregoing reasons, cavalry should not give way to a headlong pursuit after a successful charge, unless its supports are at hand; and, in cases where a charge is made without supports, a portion only should engage in pursuit, the rest being rallied to form a support.
21. Cavalry is seldom called on to use firearms. When on out-post service, or acting on the defensive on ground unfavorable to charging, a portion of the force may be dispersed as flankers, to hold the enemy in check by their fire. In this case their movements are regulated in the same wav as other skirmishers.
22. Defence. The defensive qualities of cavalry lie in the offensive. A body of cavalry which waits to receive a charge of cavalry, or is exposed to a fire of infantry, or artillery, must either retire or be destroyed. The essential quality of cavalry renders its services invaluable in retreats where the enemy pursues with vigor. In such cases it should be held in constant readiness to take advantage of every spot favorable to its action, and, by short and energetic charges, force the enemy to move with circumspection.
23. Attack Against Infantry. So long as infantry maintains its position firmly, particularly if the ground is at all unfavorable to the movements of cavalry, the chances are against a successful attack by the latter. Cavalry- should therefore either wait patiently until a way is prepared for its action, by a fire of artillery on the enemy’s infantry; or until the infantry has become crippled and exhausted by being kept in action for some time; or else, watching its opportunity, make a charge whilst the infantry is in motion, so as to surprise it before it can form to receive the attack. Cavalry should direct its charge on that point of the enemy’s infantry where it will itself be exposed to the least column of fire. If the infantry is in line, the charge should be made on one of its flanks; if in square, on one of the angles of the square; and when several squares are formed, so as to afford mutual support by their fire, selecting the squares on the flanks as most vulnerable, from their position.
24. The formation usually recommended for charging against squares, is that of three squadrons in line at double distance; the leading squadron being followed by the others, either directly in its rear, or else the squadrons may be formed in echelon, successively overlapping each other by about the front of a platoon. The angle of the square is charged by each squadron in succession, if the charge of the one preceding it fails, the repulsed squadrons each wheeling to the right or left, on retiring, to leave the way clear for its successor. A fourth squadron in column follows those in line, to surround the square and make prisoners if it should be broken by the charge.
25. To draw the fire of the infantry before charging, a few skillful flankers may be thrown forward, to open a fire on the square. Stratagem may also be tried, by moving along the front of the infantry, at some 400 paces, and then charging, if it is tempted to throw away its fire at this distance. In an attack where several squares are in line, if one fires to second another, it should be instantly charged.
26. Attack Against Artillery. In attacks against artillery, the detachment of cavalry should be divided into three bodies — one-fourth of the detachment being charged with carrying the guns, one-half to attack the supporters of the battery, and the remaining fourth acting as a reserve, to cover the parties in advance from an offensive movement against their flanks or rear. The party to secure the guns make their attack in dispersed order, and endeavor to gain the flanks of the battery. “When the battery has a fair sweep over the ground along which they must advance, they should, by manoeuvring and false attacks, try to confuse the artillerists, and draw their fire before making their charge.”
The attack against the support of the battery will be directed in the usual manner — the party manoeuvring to gain their flanks.
50. The cavalry, posted in rear of the infantry, should occupy ground upon which it can make effective charges to support the infantry when pressed by the enemy.
58. The cavalry must be in readiness, from its position, to act promptly, either against any attempt upon the flanks of the infantry, or to profit by any faults, or disorder of the enemy. If the enemy throws forward small detachments without supporting them properly, or advances his main line without securing his flanks, or shows symptoms of confusion in his infantry, the opportunity should not be lost by the cavalry. In all movements of the infantry, either in advancing or retiring, the cavalry should be at hand to cover it from a sudden attack.
59. If the enemy is beaten off, pursuit is made, either by the cavalry or by detachments of infantry, according to the features of the ground, whilst the main-body is promptly rallied, and placed in position to receive the enemy should the attack be renewed.
83. As cavalry can only act, under such circumstances in small detachments, the main body of it will take position to the rear, to cover the retreat of the other troops from the forest, and check the assailant in debouching from it.
91. There is here seldom any field of action for cavalry; the main portion of this force will therefore be kept to the rear, occupying the points of junction of the passes. Small detachments of dragoons may occasionally do good service in front, making charges, or fighting on foot, as the opportunity offers.
252. In moving forward to the attack, the troops should be kept well in hand for mutual support. The artillery and cavalry should avail themselves of all covers presented by the ground, to avoid exposure to the enemy’s artillery. The artillery should reserve its fire until it can open with a decided effect to clear the way for the action of the main body, leaving to the skirmishers to push forward, and by their fire drive the enemy from his covers. If, however, there are points from which the enemy cannot be well dislodged without the aid of artillery, it should be brought early into action, to avoid the bloodshed of unavailing attacks of the infantry. In no case should the artillery be isolated, but always covered by a strong escort; otherwise it might at any moment fall into the enemy’s hands.
253. In attacks of the character in question, where the skirmishers play so important a part, they will be required to resort frequently to the bayonet, to dislodge the enemy fully from his covers; whenever an opportunity offers, some cavalry should he at hand to take advantage of the retreat of the enemy when driven from such points.
254. The cavalry in its charges, however dashingly made, should use due circumspection, and not venture too far in a headlong pursuit, for fear of being brought up suddenly by the enemy, advantageously posted to profit by such faults.
A careful comparison of these rules with Napoleon’s Maxims of War will show the direct link. Mahan’s teaching closely track Jomini’s (but Jomini’s teachings do not address specific cavalry tactics). However, by 1861, these rules proved unworkable. We will explore the reasons why in the next part of this series.