Resigning his commission of lieutenant in the United States Cavalry at the beginning of the war, he had joined Johnston in the Valley, and impressed that officer with a high opinion of his abilities as a cavalry officer; proceeded thence to Manassas, where he charged and broke a company of "Zouave" infantry; protected the rear of the army when Johnston retired to the Rappahannock, and bore an active part in the conflict on the Peninsula.

In person he was of medium height; his frame was broad and powerful; he wore a heavy brown beard flowing upon his breast, a huge mustache of the same color, the ends curling upward; and the blue eyes, flashing beneath a "piled-up" forehead, had at times the dazzling brilliancy attributed to the eyes of the eagle.

Fond of movement, adventure, bright colors, and all the pomp and pageantry of war, Stuart had entered on the struggle with ardor, and enjoyed it as the huntsman enjoys the chase.
Young, ardent, ambitious, as brave as steel, ready with jest or laughter, with his banjo-player following him, going into the hottest battles humming a song, this young Virginian was, in truth, an original character, and impressed powerfully all who approached him.
One who knew him well wrote: "Every thing striking, brilliant, and picturesque, seemed to centre in him.

The war seemed to be to Stuart a splendid and exciting game, in which his blood coursed joyously, and his immensely strong physical organization found an arena for the display of all its faculties.

The affluent life of the man craved those perils and hardships which flush the pulses and make the heart beat fast.