Battle at the HYDRA Siberian Facility

The Battle in the HYDRA Siberian Facility is a major battle between Captain America, Winter Soldier and Iron Man in the Siberian HYDRA Facility. Shortly after the Clash of the Avengers, Bucky Barnes and Steve Rogers flew to the facility in order to prevent Helmut Zemo from unleashing other super soldier assassins on the world, unbeknownst that they are being followed by Iron Man and Black Panther.

Clash of the Avengers and Other Events
James Buchanan "Bucky" Barnes had been framed for a bombing attack on the Vienna International Centre the day the Sokovia Accords were being signed. Barnes' friend, Captain America, brought it on himself to bring Barnes in, knowing that ordinary humans would not survive an encounter with a super soldier, especially one that had once nearly beat him to death. However, Barnes tells Captain Rogers that he does not do assassinations anymore and that the attack in Vienna was not his. A chase through Bucharest only resulted in Barnes, Captain America, Falcon, and Black Panther being arrested. All four were escorted to a Joint Counter Terrorist Centre Building; the two Avengers and Black Panther were placed in an office and had their equipment confiscated, while Barnes was heavily restrained in a mobile cell, to be psychologically evaluated.

Prior to Barnes' interrogation, Theo Broussard, the psychiatrist who was supposed to be carrying out the evaluation, was murdered by Helmut Zemo, the true perpetrator of the Vienna bombing. Zemo impersonated Broussard, and carried out the evaluation as normal until he was able to speak a trigger phrase intended to activate Barnes' Winter Soldier programming and send Barnes on a rampage; Captain America realized that "Broussard" was an impostor, but was too late to prevent the attack. After killing several Joint Counter Terrorist Centre employees and nearly killing Black Widow, Barnes attempted to escape in a helicopter, but Captain America prevented him from leaving, causing Barnes to crash it. Captain America saved Barnes from drowning after falling into the river, and Barnes' Winter Soldier programming had worn off by the time he awoke.

The Joint Counter Terrorist Centre gave Iron Man 36 hours to capture Barnes and bring in his renegade comrades. Although War Machine, Vision, Black Widow, and Black Panther agreed to help Stark, he still felt undermanned and recruited high school student Peter Parker, who Stark had managed to discover was a superhero named Spider-Man, under the pretense of giving him a educational grant under the Stark September Foundation program.

Battle
Before disappearing from the airport, Romanoff tells Stark that Barnes was framed by Zemo, and Stark later finds evidence confirming this. Stark follows Rogers and Barnes to the Siberian HYDRA facility, and is shadowed by T'Challa. They discover that the other Winter Soldiers have been killed by Zemo, who is Sokovian and wants to punish the Avengers for his family's deaths. He shows them footage revealing it was Stark's parents whom Barnes killed in 1991. Enraged to learn that Rogers was aware of this (as Arnim Zola had revealed this to both Steve Rogers and Natasha Romanoff two years prior) Stark turns on Barnes. In the resulting fight, Stark blasts off Barnes' robotic arm as Barnes is attempting to remove Stark's arc reactor. Rogers manages to use his shield to destroy Stark's arc reactor, effectively shutting down his suit. Rogers departs with Barnes and leaves his shield, built by Stark's father, behind. Satisfied that he has irreparably fractured the Avengers, Zemo attempts suicide, but is apprehended by T'Challa.

Aftermath
In the aftermath, Stark provides Rhodes with exoskeletal leg braces to let him walk again. Rogers breaks his comrades out of detainment and flees to Wakanda, where T'Challa grants them asylum and Barnes chooses to be frozen until a cure for his brainwashing can be found.