Rather, one part of the militia line retreated to the left rear of the main line, while the other part retreated to the right rear of the main line. More specifically, I believe that the militia line was divided into a left and right wing and that when the militia fell back, the left wing retreated to the left rear and the right wing retreated to the right rear.
The Planned American Retreat. 1 = Continental Light Dragoons, 2 = Mounted Militia, 3 = Right Wing of the Main Line, 4 = Continental Infantry, 5 = Left Wing of the Main Line, 6 = Right Wing of the Militia Line, 7 = Left Wing of the Militia Line, 8 = Skirmishers
The traditional view of the retreat of the militia is not supported by an examination of participant accounts. Instead, the view that the militia retreated across the front of the Continentals originated with William Johnson's 1822 history, Sketches of the Life and Correspondence of Nathanael Greene. This view also should have ended with him. Johnson had the advantage of being one of the first to write a history of the battle, and he was writing at a time when many of the participants in the battle still lived. Nevertheless, his history is wrong on many counts. Colonel Henry Lee's second history, The Campaign of 1781 in the Carolinas: With Remarks, Historical and Critical, on Johnson's Life of Greene (1824) is devoted in large part to refuting Johnson's history. For the section of his book concerned with the battle of Cowpens, Lee included excerpts from a letter by Lieutenant-Colonel John Eager Howard, one of the principal architects of the American victory, that serves essentially as a point-by-point refutation of Johnson's version of events.
Johnson: "The cavalry of Tarleton's left wing had poured upon the rear of the retreating militia. As the right of the line of militia had to traverse the whole front of the second line to reach the ground on which they were ordered to rally, they were necessarily very much exposed to this danger.
Howard: "The militia were formed in front of me, and the moment the british militia [see Note 1] formed their line they shouted and made a great noise to intimidate, and rushed with bayonets upon the militia who had not time, especially the riflemen to fire a second time. The militia fell into our rear, and part of them fell into the rear of my right flank where they afterwards renewed the action."
In other words, Howard is saying yes, the cavalry of Tarleton's left wing did attack the militia, but the militia did no such thing as retreat en masse across Howard's front. A part retreated to the rear of his "right flank where they afterwards renewed the action," and, by, extension, a part retreated to the rear of his left flank.
Johnson: "Washington flew to their assistance, and repulsing the enemy, enabled the militia to regain the tranquillity necessary for returning to a state of order. The eminence which had covered the reserve was exceedingly favourable to this purpose, and Pickens knew how to avail himself of it. Here most of them gathered round him and were soon reduced to order.
Howard: "I do not think there was such an eminence; there was a slight rise in the ground."
Howard doesn't deny that Washington aided the militia at this point or that Pickens was acting to rally the militia, but he does dispute Johnson's characterization of the terrain.
Johnson: "Apprehensive that the reserve could not be brought up in time to defend his exposed flank, or if it were, that it would leave his other flank too much exposed, Morgan dispatched an order to the militia on his right, to fall back from their right so as to form at right angles with his line, and repel the enemy's, advance upon his right flank. To effect this manoeuvre with precision and dispatch, the commanding officer ordered his men to face to the right about, and wheel on their left. The first part of the order was executed with coolness and recollection, and the militia began to move. At this point of time it was that fortune, ever hovering over fields of battle, played off that celebrated freak which at first threatened destruction to the American arms, but in a moment after, crowned them with the most signal success; Seeing the movement of the right of their line, and supposing that this was the state of things which required a retreat to the eminence in their rear, the whole American line faced about and began to move rather in an accelerating step, but still in perfect order, towards their intended second position. Howard presuming the order must have emanated from the commander, made no opposition, but bent his whole attention to the preservation of order, and encouragement- of his men. Morgan also under the impression that the movement was made under the order of Howard, and thinking favourably of it, under existing circumstances, rode along the rear of the line reminding the officers to halt and face as soon as they reached their ground. But just at that crisis they were accosted by another officer, and their attention drawn to some facts which produced an immediate change of measures."
Howard: "Seeing my right flank was exposed to the enemy, I attempted to change the front of Wallace's company, (Virginia regulars;) in doing it, some confusion ensued, and first a part, and then the whole of the company commenced a retreat. The officers along the line seeing this, and supposing that orders had been given for a retreat, faced their men about, and moved off. Morgan, who had mostly been with the militia, quickly rode up to me and expressed apprehensions of the event; but I soon removed his fears by pointing to the line, and observing that the men were not beaten who retreated in that order. He then ordered me to keep with the men, until we came to the rising ground near Washington's horse; and he rode forward to fix on the most proper place for us to halt and face about. In a minute we had a perfect line."
Johnson is describing here the unordered withdraw of Wallace's company of Virginians. Howard identifies the command and points out that they were regulars, not militia. Then he points out that the order originated not with Morgan, who with Pickens was rallying the militia, but with himself. Then he points out that he (Howard) was in control of the situation. The farcical situation that Johnson describes in which both Howard and Morgan think the retreat has been ordered by the other commander did not occur.
I could go on and on. Reading Johnson and Howard side-by-side is quite instructive. However, my concern is with the retreat of the militia. Where did Johnson obtain the erroneous idea that the militia retreated the field while crossing from right to left in front of the Continentals? My supposition is that he read earlier accounts of the battle, such as the Tarleton-Mackenzie-Hanger exchange, and attempted to reconcile the various contradictory statements in them.
Lieutenant-Colonel Banastre Tarleton said that, "A captain, with fifty dragoons, was placed on each flank of the corps... The cavalry on the right were directed to charge the enemy's left"
Lieutenant Roderick Mackenzie, however, said that, "Captain Ogilvie, with his troop, which did not exceed forty men, was ordered to charge the right flank of the enemy."
Saying that the Americans retreated from right to left, would allow both of their statements to be correct, if they referred to different points in time (the retreating militia were moving from right to left). However, this attempt to finesse Tarleton's and Mackenzie's statements makes no sense. Mackenzie was not adding detail to Tarleton's comments but rather offering a corrective to them. Johnson should have understood as much.
Unfortunately, despite the rhetorical drubbing that Howard delivered, historians remained respectful of Johnson's version of events and his description has had a very large influence on subsequent histories of the battle of Cowpens.
1. The word "militia" was seemingly written in error. If it was not, then by "british militia," Howard may have meant the British Legion infantry, whose members were Loyalists. If the latter interpretation is correct then this suggests that the British Legion infantry were most directly opposed to the Continentals.
Edwin Bearss' 1967 Battle of Cowpens: A Documented Narrative and Troop Movement Maps
William Johnson's 1822 Sketches of the Life and Correspondence of Nathanael Greene
John Moncure's online history of the battle, The Cowpens Staff Ride and Battlefield Tour, includes a complete transcription of Howard's letter, plus the statements by Tarleton and Mackenzie.