Mosby certainly recognized his physical shortcomings, and worked to overcome them. Late in life he wrote: "In my youth I was very delicate and often heard that I would never live to be a grown man. But the prophets were wrong, for I have outlived nearly all the contemporaries of my youth" (Memoirs, p.5). Indeed, Mosby's small size served to stimulate his aggressive nature, through which he could maintain his sense of honor among bigger men -- a struggle that could even be interpreted as an anthropomorphic metaphor for the Confederacy itself, outmatched in virtually every quantifiable category during the Civil War.
The small size of Mosby reinforced the popular wartime image of a David with the ability to slay any Goliath who came in his path. As a second-year student at the University of Virginia in 1852, this image first gained validity. George Turpin, a "big, tough medical student" got into a disagreement with the "mild and frail" Mosby (Daniels, pp.9,12). Soon afterwards Mosby carried a loaded pistol to confront Turpin and settle their argument. Words were exchanged, and soon Turpin fell to the floor with a bullet through his neck. Local authorities imprisoned the young student, but he was released shortly afterwards, pardoned by Virginia Gov. Joseph Johnson who was convinced of Mosby's alleged act of self-defense. Johnson's decision also came after 300 citizens attested to Mosby's good character and several local physicians wrote to declare that "Mosby was constitutionally consumptive, that he was in a precarious state of health, and that imprisonment for a year would incur the risk of his life" (Jones, p.26). The University expelled Mosby, yet the community excused him. The incident points to two conditions of antebellum Southern society: a leniency in matters of defending one's reputation, and an allowance for even slight individuals to take part in the code of honor.
When Mosby first joined Gen. J.E.B. Stuart's cavalry, he was seen merely as a "slouching scout." But in due course, after having acquired his own band of rangers, he took on a new air, donning a feather in his cap and two pistols held at his sides. "Mosby himself looked as elegant as the plumed General. ... The uniform he wore was immaculate from polished boots to the plume like Stuart's in his hat" (Daniels, p.83). Thirty years after the war another admirer, George Cary Eggleston, spoke about Mosby's appearance: "In stature he was of medium height and weight. On foot he was in no way conspicuous, but on his horse he was every inch a cavalier. Sun-burned, weather-beaten and swarthy, he had a singularly winning countenance. It had gentleness as well as determination in it, delicacy as well as daring" (5/2/1897). Mosby biographer Virgil Carrington Jones described Mosby's appearance with the appropriate respect due a war hero, albeit a small one: "His slight frame of medium height was muscular, supple, vigorous, capable of great activity. His hair was sandy, his face clean cut, his lips like a cameo. He had features that were large and youthful. His eyes did not glance; they pierced" (p.13).
As time went on and Mosby's legend grew, descriptions of him improved accordingly. Although Mosby at 60 probably was no larger than at the age of 19, writers became ever more glowing when discussing the former raider's presence. By the time of his death at age 81, one obituary read: "His home lay across the Potomac, at Warrenton, Va., but he was often seen in Washington, his white hair and strong Roman features making him a picturesque figure on the streets or lecture platform."