Here is the full text of the horsebreaking story, as it appeared in James Parton's Life of Andrew Jackson:

"As soon," wrote the old tory messenger, "as I came in view of the British lines I hastened to deliver myself up to the nearest patrol, informing him that I was the bearer of important dispatches from Lord Cornwallis to Colonel Tarleton. The guard was immediately called out, the commander of which, taking me in charge, carried me at once to Tarleton's marque. A servant informed him of my arrival, and returned immediately with the answer that his master would see me after a while, and that, in the meanwhile, I was to await his pleasure where I then was[.] The servant was a grave and sedate looking Englishman, between fifty and sixty years of age, and informed me that he had known Colonel Tarleton from his earliest youth, having lived for many years in the family of his father, a worthy clergyman, at whose particular request he had followed the colonel to this country with the view that, if overtaken by disease and suffering in his headlong career, he might have some one near him who had known him ere the pranksome mischief of the boy had hardened into the sterner vices of the man. 'He was always a wild blade, friend,' said the old man, 'and many a heart-ache has he given us all; but he'll mend in time, I hope.' Just then my attention was attracted by the violent plungings of a horse which two stout grooms, one on each side, were endeavoring to lead toward the spot where we were standing. He was a large and powerful brute, beautifully formed, and black as a crow, with an eye that actually seemed to blaze with rage at the restraint put upon him. His progress was one continued bound, at times swinging the grooms clear from the earth as lightly as though they were but tassels hung on his huge Spanish bit, so that with difficulty they escaped being trampled under foot. I asked the meaning of the scene, and was informed that the horse was one that Tarleton had heard of as being a magnificent animal, but one altogether unmanageable; and so delighted was he with the description, that he sent all the way down into Moore county, where his owner resided, and purchased him at the extravagant price of one hundred guineas; and that, moreover, he was about to ride him that morning. 'Ride him!' said I, 'why, one had as well try to back a streak of lightning. The mad brute will certainly be the death of him.' 'Never fear for him,' said my companion, 'never fear for him. His time has not come yet.' By this time the horse had been brought up to where we were; the curtain of the marque was pushed aside, and my attention was drawn from the savage stud to rivet itself upon his dauntless rider. And a picture of a man he was! Rather below the middle height, and with a face almost femininely beautiful. Tarleton possessed a form that was a perfect model of manly strength and vigor. Without a particle of superfluous flesh, his rounded limbs and full broad chest seemed molded from iron, yet, at the same time, displaying all the elasticity which usually accompanies elegance of proportion. His dress, strange as it may appear, was a jacket and breeches of white linen, fitted to his form with the utmost exactness. Boots of russet leather were half way up the leg, the broad tops of which were turned down, the heels garnished with spurs of an immense size and length of rowel. On his head was a low-crowned hat, curiously formed from the snow-white feathers of the swan, and in his hand he carried a heavy scourge with shot well twisted into its knotted lash. After looking around for a moment or two, as though to command the attention of all, he advanced to the side of the [p84] horse, and, disdaining the use of the stirrup, with one bound threw himself into the saddle, at the same time calling on the grooms to let him go. For an instant the animal seemed paralyzed; then, with a perfect yell of rage, bounded into the air like a stricken deer.

"The struggle for mastery had commenced -- bound succeeded bound with the rapidity of thought; every device which its animal instinct could teach was resorted to by the maddened brute to shake off its unwelcome burden -- but in vain. Its ruthless rider proved irresistible, and clinging like fate itself plied the scourge and rowel like a fiend. The punishment was too severe to be long withstood, and at length, after a succession of frantic efforts, the tortured animal, with a scream of agony, leaped forth upon the plain, and flew across it with the speed of an arrow. The ground upon which Tarleton had pitched his camp was an almost perfectly level plain, something more than half a mile in circumference. Around this, after getting him under way, he continued to urge his furious steed, amid the raptures and shouts of the admiring soldiery, plying the whip and spur at every leap, until wearied and worn down with its prodigious efforts, the tired creature discontinued all exertion, save that to which it was urged by its merciless rider.

"At length, exhausted from the conflict, Tarleton drew up before his tent, and threw himself from the saddle. The horse was completely subdued, and at the word of command followed him around like a dog. The victory was complete. His eye of fire was dim and lusterless, drops of agony fell from his drooping front, while from his laboring and mangled sides the mingled blood and foam poured in a thick and clotted stream. Tarleton himself was pale as death, and as soon as he was satisfied of his success, retired and threw himself on his couch. In a short time I was called into his presence, and delivered my dispatches. I have witnessed many stirring scenes, both during the Revolution and since, but I never saw one half so exciting as the strife between that savage man and savage horse."

[Source: James Parton, Life of Andrew Jackson, 3 vols. (New York: Mason Brothers; 1860), 1:82-84.]