​Staff Sergeant Reckless was a decorated war horse who held official rank in the United States military. During the Korean War, she carried ammunition to the front lines and rescued wounded soldiers
 
She was purchased by members of the United States Marine Corps in October 1952 for $250 from a young Korean boy. The horse's breeding was thought to be primarily Mongolian though she did have some features, particularly the shape of her head, that were similar to horses of Thoroughbred lineage. She was small, standing only 14 hands and weighing 900 pounds. The Marines renamed her "Reckless" as a contraction of the name of the Recoilless rifle and a nod to the daredevil attitude associated with those who used the gun.

Reckless was taught battlefield survival skills such as how not to become entangled in barbed wire and to lie down when under fire.  She learned to run for a bunker upon hearing the cry, "incoming!" The platoon called it her "hoof training" and "hoof camp". The horse was initially kept in a pasture near the encampment. Reckless had a gentle disposition and soon developed such a rapport with the troops that she was allowed to freely roam about the camp and entered tents at will, sometimes sleeping inside with the troops, and even lying down next to Latham's warm tent stove on cold nights. She was fond of a wide variety of foodstuffs, entertaining the platoon by eating scrambled eggs and drinking Coca-Cola and beer. Food could not be left unattended around her. She was known to eat bacon, buttered toast, chocolate bars, hard candy, shredded wheat, peanut butter sandwiches and mashed potatoes. However, Mitchell advised the platoon that she not be given more than two bottles of Coke a day. Her tastes were not confined to foodstuffs; she once ate her horse blanket, and on another occasion ate $30 worth of Latham's winning poker chips.
 
Reckless's baptism under fire came at a place called Hedley's Crotch, near the villages of Changdan and Kwakchan. Though loaded down with six recoilless rifle shells, she initially "went straight up" and all four feet left the ground the first time the Recoilless Rifle was fired. When she landed she started shaking, but her handler calmed her down. The second time the gun fired she merely snorted, and by the end of the mission that day, she appeared calm and was seen trying to eat a discarded helmet liner. She even appeared to take an interest in the operation of the weapon. When learning a new delivery route, Reckless would only need someone to lead her a few times. Afterwards she would make the trips on her owm