According to legend, the brutal militia raid on the family farm in 1863, in which Jesse James may have been beaten and his stepfather was briefly hung, led Jesse to join the guerrillas in order to get revenge. In reality, a year passed between this event and his enrollment in the bushwhacker ranks at the tender age of sixteen. When he did join, the Union forces in Clay County consisted of the Paw-Paw militia, two regiments that included numerous former Confederate soldiers, organized primarily to prevent retaliation from Kansas for the Lawrence massacre. In other words, local secessionists were facing the lowest danger of harrassment than at any time since the end of 1861. What motivated Jesse was a commitment to the Confederate cause as much as any thirst for revenge. He began his military career as a member of what was, in essence, a death squad, led by Fletch Taylor and Archie Clement, that went from house to house to murder Unionist civilians in Jesse's own neighborhood.

This photo is believed to have been taken in Platte City during a brief Confederate occupation of the town in 1864. Jesse carries the multiple revolvers favored by the bushwhackers, who relied on the weapon's rapid rate of fire to overwhelm the enemy in close-range ambushes. The cap-and-ball revolvers were tiresome to load, however, and frequently jammed, so the guerrillas routinely carried three or four at a time. He also wears a "guerrilla shirt," a loose pullover with deep breast pockets for lead balls and percussion caps.