The Attack on HYDRA Headquarters was a strategic incursion established by the United States Army and the Strategic Scientific Reserve to bring down HYDRA before the Red Skull could unleash weapons of mass destruction upon the United States.
Captain America, the Howling Commandos, the United States Army, and the Strategic Scientific Reserve destroyed many HYDRA bases over Europe, thwarting many of their attacks. Unable to find Johann Schmidt and his secret headquarters, the commandos went to attack the Schnellzug EB912, a train transporting Arnim Zola.
In the attack, Gabe Jones succeeded in capturing Zola, but Bucky Barnes, Steve Rogers' best friend, fell off the train and down the mountain and was presumed dead. Zola eventually told Colonel Chester Phillips that Red Skull was planning to attack the United States of America and also gave him the location of HYDRA Headquarters. The plan to finally take down HYDRA once and for all had begun.
Captain America approached HYDRA Headquarters on his motorcycle. Before reaching the gate, Rogers was spotted by six HYDRA soldiers on motorbikes. Rogers used his motorcycle's weapons to kill the soldiers and continued to the gate. With the gate blockaded by a HYDRA Mini Tank and several cannons, Rogers attached his shield to the front of his motorcycle to block the cannon fire before destroying the armored vehicle with his motorcycle's rocket launchers. After jumping the gate and setting the motorcycle's self-destruct, Rogers pointed it towards the door and jumped off. The motorcycle successfully blew the door and Rogers began to fight the HYDRA soldiers. Taking out several soldiers, Rogers was cornered by soldiers with flamethrowers, surrounded, and forced to surrender.
The soldiers took Rogers to Red Skull, who planned to kill him but was interrupted by the Howling Commandos zip-lining through the window. Red Skull retreated down the hall while the Commandos killed the HYDRA soldiers in the room. James Montgomery Falsworth tossed Rogers his shield and he chased Red Skull while Jim Morita radioed Colonel Chester Phillips to begin the ground assault. The Strategic Scientific Reserve troops took out the HYDRA soldiers outside and entered the base. Rogers was cut off from Red Skull by a HYDRA soldier with a flamethrower but was saved by Peggy Carter.
Rogers followed Red Skull to the hanger bay but he had already boarded the Valkyrie and began to take off. Rogers attempted to catch the plane on foot but was unable to catch it. Phillips and Carter arrived in Johann Schmidt's Coupe and picked up Rogers. Phillips drove the car up to the landing gear and Rogers kissed Carter before jumping onto the plane. Phillips slammed on the brakes and managed to stop the car just before it fell off the cliff. The SSR troops defeated the remaining HYDRA personnel and captured the base.
Captain America boarded the Valkyrie while the Strategic Scientific Reserve secured HYDRA Headquarters. Rogers successfully fought his way through the aircraft, battling against Red Skull until he was teleported away by the Tesseract. Seeing no other option to prevent the plane from reaching the United States of America, Rogers deviated the Valkyrie and crashed it in the Arctic.