Participant accounts provide very strong evidence that the militia were assailed during the battle by the British dragoons. A statement in British commander Lieutenant-Colonel Banastre Tarleton’s memoir -- “The cavalry on the right were directed to charge the enemy's left" -- is commonly understood to be his way of saying that he dispatched a troop of dragoons to attack the militia during their retreat. Therefore, my position -- that the militia simultaneously retreated to both the left and right rear of the main line -- would seem to be problematic. Why would Tarleton only dispatch a troop of dragoons to attack the militia on the American left when there was also a large body of militia on the American right?
Tarleton indicated that he stationed a troop of dragoons on both of his flanks at the onset of the battle and Lawrence Babits, in A Devil of a Whipping, argued that both of these troops saw combat during the battle. Babits specifically identified the troop on the British right as the company of 17th light dragoons under the command of Lieutenant Henry Nettles, and the troop on the British left as the company of British Legion dragoons under the command of Captain David Ogilvie. I find these arguments convincing.
Babits has both Nettles and Ogilvie in action not long after the militia began their flight. In his account, Nettles on the British right attacked the front-line militia who were mostly (although not entirely) reforming in the left rear of the American main line (his account is fairly conventional on this point; cf. Flight of the Militia - Part 1). He also claimed that Ogilvie, on the British left, helped drive off Major Joseph McDowell’s North Carolinians.
My review of the source documents has convinced me that Babits is correct about the occurrence of separate charges by Nettles and Ogilvie. That two charges occurred is indicated in reliable sources. Major Joseph McJunkin noted that "Tarleton then made a charge on the right & left wings, treading & cutting till he got in the rear of Howard's command, when Col. Washington made a charge upon him." Major-General François-Jean de Chastellux also learned that both flanks were targeted. He wrote that the British cavalry “endeavoured to turn the flanks of General Morgan's army, but were kept in awe by some riflemen, and by the American horse detached by Colonel Washington, to support them, in two little squadrons.”
Other accounts explicitly mention a British cavalry attack on either the American left flank or right flank, further indicating that both flanks were attacked. One mounted militiaman, Jeremiah Dial, remembered that the British cavalry "broke through the leftwing of the Malitia," while another, Thomas Young remembered when "the British cavalry had charged the American right."
However, I take a different view about the timing of and targets of those charges. Specifically, I believe that a) the first British cavalry charge was made by Ogilvie's company, and b) that the British cavalry charges were directed against the retreating militia.
The accounts quoted above do not suggest that the retreating front-line militia were the targets of these attacks. The flanks, rather, seem to be extensions of the main line. In McJunkin's account, the wings are broken through before the cavalry reaches the American rear where the American militia were rallying.
A comparison of the several British accounts of the battle suggest that the first British cavalry charge was directed against the right wing of the American main line.
Tarleton said that "The cavalry on the right were directed to charge the enemy's left," but Lieutenant Roderick Mackenzie corrected him, saying "Captain Ogilvie, with his troop, which did not exceed forty men, was ordered to charge the right flank of the enemy."
Tarleton did seem to have the American right flank in mind as a target. He mentioned in his description of the American deployment that his reserve infantry, the 71st Foot, was placed on behind the far left of the British line, rather than in the center. For a later point in the battle, when the attack on the American main line was underway, he described his intention to envelop the right of the main line:
"Lieutenant-colonel Tarleton thought the advance of the 71st into line, and a movement of the cavalry in reserve to threaten the enemy's right flank, would put a victorious period into the action."
Moreover, British and American accounts suggest that this charge by Ogilvie was successful insofar as it resulted in the rout of the right wing (see: The Main Line: The Right Wing Collapses for details).
However, Tarleton also claimed that these dragoons were "drove back by the fire of the reserve, and by a charge of Colonel Washington's cavalry." My belief is that when Ogilvie's dragoons succeeded in breaking through the right wing of the main line, they then ran into (most likely unexpectedly) into the right wing of the front line, which would have been at that moment reforming a short distance nearby.
Ogilvie's Attack. 1 = Continental Light Dragoons, 2 = Mounted Militia, 3 = Right Wing of the Main Line (broken by Ogilvie's charge), 4 = Continental Infantry, 5 = Left Wing of the Main Line, 6 = Right Wing of the Militia Line (reforming), 7 = Left Wing of the Militia Line (reforming), 9 = British Front Line, 10 = Captain David Ogilvie's Company, 11 = Other British Legion Dragoons, 12 = 17th Light Dragoons, 13 = 71st Foot, 14 = Main British Legion Dragoon Reserve.
This second encounter, between Ogilvie's dragoons and the reforming militia is what gave rise to the impression that the retreating militia had been targeted. In McJunkin's words, "Then there is a charge of the dragoons even past the line of regulars after the retreating militia. Numbers are cut down." This "reserve" (Tarleton's term) was significantly larger than the force Ogilvie had just routed and they, with the assistance of the American cavalry, defeated Ogilvie's attack. Noteworthy is that McJunkin and most of the would-be pensioners mentioning a British cavalry attack were in the units I've located on the right wing of the militia line and that would have been in the line of Ogilvie's charge (see The Militia Line: Composition and Organization; Flight of the Militia - Part 1).
Marg Baskin's Banastre Tarleton website has a transcription of Tarleton's and Mackenzie's accounts of the battle.
Lawrence Babits' 1998 A Devil of a Whipping: The Battle of Cowpens is available through amazon.com.
This issue (.pdf file) of The Southern Campaigns of the American Revolution magazine includes an article by Will Graves that provides a thorough treatment of McJunkin's statements.
François-Jean de Chastellux's 1787 Travels in North-America, in the Years 1780, 1781, and 1782.