James Buchanan "Bucky" Barnes is the protégé and childhood friend of Captain America, and a member of an elite special unit of Allied soldiers formed in World War II known as the Howling Commandos. He was assumed dead after falling off of Zola's Train but somehow survived to return as The Winter Soldier.
Bucky was orphaned at an early age and had been living in an orphanage ever since. During a regular day, he noticed a skimpy, weak kid getting beaten up by some bullies. He stepped in and saved the kid, who introduced himself as Steve Rogers. Years later, during an art class Bucky and Steve found out that America has joined the Second World War. Over the next two weeks he trained Steve at Goldie's Boxing Gym. They visited US Recruiting and Induction Center in New York City where Steve was classified as 4F and rejected from service. But Bucky was later enlisted in the Army and assumed the title of Sgt. Barnes.
The day before his shipment out to England, Bucky saved his friend Steve from being beated up by a bully. Bucky and Steve then went to the Stark Expo on a double date, though Bucky was having fun, Steve was more interested in enlisting for the fifth time. Despite Bucky's protests Steve went through with it but said goodbye to Bucky before doing so. Bucky and his unit the 107th then shipped to England the next day.
A year later, Bucky and his unit consisting of 200 men went up against a Nazi sup group named HYDRA lead by Johann Schmidt at the orders of the SSR but 150 of the men were either killed or captured while 50 barley escaped. Bucky and the Howling Commandos were among the captured. Bucky was taken to a prison where he was forced to work to design rockets called Valkyries, but it eventually became too much and he was taken to an isolation clinic for interrogation. But a few days later Steve (who had become Captain America) infiltrated the base, freed the prisoners and eventually Bucky too. During the escape Bucky and Steve encountered Schmidt and Zola but were able to escape them and the facility before it blew and walked all the way back to base, 30 miles out.
In the winter of 1944, Bucky and Captain America boarded a HYDRA train carrying Arnim Zola. Bucky takes Captain America's shield and blocks him while he's down, but clearly not having the upper body strength to hold on to it when getting hit it shoots him out the side of the train. He was hanging on to a rail on the outside of the train, but it broke before Cap was able to save him, which resulted in Bucky falling into an icy river below.
More than seventy years after the end of World War II, Steve Rogers, having been awakened in the 21st century, studied S.H.I.E.L.D.'s files about the Commandos. In Bucky's file, he was reported as "Missing in action", implying that he may be still alive in the modern age.
