Winter Soldier Program

"Sergeant Barnes... the procedure has already started. You are to be the new fist of HYDRA!"

- Arnim Zola

The Winter Soldier Program was a top secret Soviet project started by Arnim Zola that involved brainwashing American hero James Buchanan Barnes and turning him into a deadly assassin for HYDRA using a serum similar to the Super Soldier Serum.

Barnes' Death and Rebirth
In the winter of 1945, Bucky Barnes and Captain America boarded a HYDRA train carrying Arnim Zola during a Strategic Scientific Reserve operation. During the fight with HYDRA, the side of the train car was destroyed. A second blast from the HYDRA operative's weapon threw Barnes out of the train. He managed to grab hold of the side of the train but lost his grip before Captain America could pull him back in. Barnes survived the fall because of Zola's version of the Super Soldier Serum, first given to Barnes in 1943 while he was imprisoned at the Austrian HYDRA Weapons Facility, but he lost his left arm. He was later found by Soviet soldiers.

Zola's Experiments
Zola continued his experiments on Barnes after he joined Operation Paperclip and became a scientist for S.H.I.E.L.D. He replaced Barnes' lost arm with a metal prosthetic and subjected Barnes to multiple mind control methods meant to keep him under their command. Over time, he lost all his memories of his former life and became one of the world's deadliest assassins.

Assassinations
Over the next 50 years, HYDRA used Barnes as a weapon to eliminate their targets and enemies, including the Assassination of Howard and Maria Stark to recover the former's recreated version of the Super Soldier Serum.

Barnes was kept in suspended animation in a Cryostasis Chamber when not on a mission to prevent aging or any mental or physical deterioration. His mind was frequently wiped using HYDRA technology to prevent him from fighting HYDRA's control. He was responsible for many assassinations, including those of politicians and scientists. He became a legend and ghost story in the intelligence community.

New Recruits
In 1991, after Howard Stark managed to obtain or recreate the Super Soldier Serum, HYDRA sent Barnes to retrieve the serum from Stark's car and kill all occupants. While transporting the serum to give to the United States Government, Howard and his wife Maria were killed by Barnes and the serum was stolen and brought to HYDRA's Siberian Facility. HYDRA's top kill squad was chosen to be test subjects for the serum; one woman and four men were transported to the base in Siberia. At first, the injection led to extreme pain for the subjects, but soon after they were given enhanced physical attributes even greater then that of Barnes himself. However, the change left them erratic and unruly and they were therefore deemed too risky to be deployed in the field. The five new super soldiers were put in cryostasis chambers, where they remained frozen until their deaths at the hands of Helmut Zemo in 2016.

Project Insight
In 2014 Alexander Pierce awoke Barnes for HYDRA's plan to wipe out over a million targets using S.H.I.E.L.D.'s Helicarriers. He was assigned to assassinate Nick Fury, and a day later, he was also sent to stop Natasha Romanoff and Steve Rogers before they could prevent the launch of the three HYDRA Helicarriers that would allow HYDRA to eliminate their targets immediately.

Barnes' Desertion
"Your name is James Buchanan Barnes. I'm not going to fight you; you're my friend."

- Captain America

Barnes fought Rogers on a Helicarrier during the Battle at the Triskelion. Once Rogers had changed the targeting data so the Helicarriers would target each other instead of people, he stopped fighting and told Barnes, "I'm with you 'til the end of the line," a phrase that Barnes had said to Rogers after Sarah Rogers's funeral in 1941. The phrase triggered Barnes' memory, and when the Helicarrier crashed and Rogers fell into the Potomac, Barnes went after him and pulled Rogers out of the river so he wouldn't drown. Though he left Rogers on the river bank, he visited the Captain America exhibit at the Smithsonian Institution a few days later and saw his own memorial.

End of the Program
In 2016, Helmut Zemo, a former officer of the Sokovian military, arrived to the Siberian HYDRA Facility, where Rogers and Barnes assumed he intended to "wake" up the other Winter Soldiers and attempt to use them. When Barnes, Rogers and Stark arrived there, they found out that Zemo killed them all.

Super Soldier Serum
During World War II, Arnim Zola created a serum similar to Captain America's. It presumably enhanced Barnes' body to beyond human limits, in terms of strength, senses, speed, agility, mental faculties, stamina, durability, longevity and self-healing speeds. This made the subject physically super-human, while unlike the original Super Soldier Serum, it did not enhance personality or bring such traits into physical manifestations. As for the other subjects, Winter Soldier had stolen a container with bags of another version of the Super Soldier Serum handled by Howard Stark, who he murdered along with his wife. This serum caused an excruciating transformation without the need of Vita Rays, which afterward left the subject physically more powerful than even the original Winter Soldier, as one subject was shown to overpower and send the latter flying during a sparring match. Not even with his metal arm could Barnes defeat the new super human. However, the serum enhanced the aggression in these volunteers, and they turned on other HYDRA soldiers. They were eventually overpowered and placed in suspended animation.

Bionic Arm
Barnes' left arm was partially lost when he fell off Zola's train and was completely removed when he was found by the Soviet Army. It was replaced by a metal bionic arm that is very durable and additionally enhanced Barnes' already enhanced strength. However, it could still be damaged by Captain America's Vibranium shield, and Black Widow was able to shut the arm off temporarily using a Taser Disk. Iron Man eventually destroyed the arm with his repulsor blasts. A red Soviet star was painted on the shoulder. However, only Barnes possessed one such metal arm, while the other was completely organic.

Mental Manipulation
To make Barnes the ultimate weapon, scientists had to erase the man he was so they could rebuild him as they saw fit. The Memory Suppressing Machine was able to erase three decades worth of memories from Barnes' mind, a procedure that caused him excruciating pain. He usually had his mind "wiped" after each reawakening from the cryostasis chamber. Even after dozens of memory wipes, his memories returned with triggers provided by his best friend Steve Rogers. The series of code words to make make Barnes into a compliant killing machine were: Longing, Rusted, Seventeen, Daybreak, Furnace, Nine, Benign, Homecoming, One and Freightcar. Once these words were spoken aloud Barnes would would say "ready to comply" and would become under the control of whomever spoke the words.

Cryostasis Chamber
These chambers use cryogenic technology to freeze the person placed inside it and put them in a "hibernation," preventing aging and the deterioration of one's mind or body. These chambers were designed to give HYDRA complete control, allowing HYDRA to freeze or defrost their assets whenever they wanted. The subjects other than Barnes were seemingly never woken, as HYDRA abandoned the facility they were kept at, while Helmut Zemo soon found it and shot them all dead in their sleep.