When the war between the states broke out, Jack's older brother Orville joined the Confederate army as a lieutenant under the command of Col. J.E.B Stuart. Jack, then 14, immediately volunteered his services but was, to his great disappointment, denied because of his age. After several attempts, he was finally accepted into the army when he was l6 and was assigned to his brother's regiment.

Jack quickly gained renown as a scout of ability and bravery, working directly under Stuart, and was soon to be widely known as the "Boy Scout of the Confederacy." Many times he would act as a spy moving among the Union troops as a chicken peddler or some other kind of tradesman obtaining information about the enemy. Little was he to know that within the next 10 years his best friends and saddle-mates would be former Union soldiers.