The HYDRA Headquarters was an important strategic military base in the 1940s, carved out deep within one of the mountains of the Alps, which served as HYDRA's foremost stronghold during World War II. The base included an expansive airfield carved within the mountain from which the HYDRA super-bomber Valkyrie was launched.
Johann Schmidt's Hideout
In 1940, Johann Schmidt tested Abraham Erskine's Super Soldier Serum on himself. The serum made him stronger, but it also disfigured his face as the result, and he became known as the Red Skull. As a small reward for his injuries, Adolf Hitler gave the base to Schmidt, who turned it into the headquarters of HYDRA. In the base, HYDRA's best scientists worked on developing new weapons for the Third Reich. However, Schmidt saw his new post more as an exile than the reward.
Development of HYDRA's Arsenal
In 1942, Schmidt brought the Tesseract, an object of unlimited power which he found in Norway, into the base, where HYDRA's top scientist Arnim Zola was ordered to use a device he invented in order to harness the power of the Tesseract. Schmidt placed the Tesseract inside the machine, and Zola began to transfer the energy from the Tesseract into battery cells. However, Schmidt was not satisfied with a halfway transference and managed to make a complete stable transference to power Zola's advanced scientific designs.
Sometime later, Schmidt posed for a portrait when Arnim Zola came to ask about what he planned to do with Abraham Erskine after finally discovering his whereabouts. As Zola was sure that Erskine wouldn't manage to reproduce the serum for the allies, he viewed unnecessary to kill him, but Schmidt answered that he intended to kill Erskine as his serum was the only possible defense for the Allies against HYDRA's power, and without him, HYDRA's victory was secure.
In 1943, Adolf Hitler sent Hutter, Roeder and Schneider, to question Schmidt about HYDRA's failure to deliver weapons to the German armies, and his incursion in Norway. Schmidt, considering himself as exiled in his own facility, invited the gentlemen to review his work. Being mocked by the officers, who considered his theories as "magic", Schmidt armed his prototype Tesseract-powered pulse cannon while assuring that HYDRA was gathering an arsenal to destroy his own enemies.
The officers took Schmidt's words as a sign of madness and discovered that Schmidt intended to destroy Berlin and overthrow Hitler. Schmidt being menaced for his insurrection, vaporized the three officers to silence them, disassociating HYDRA from the Third Reich. Arnim Zola and the other scientists that witnessed these events immediately swore allegiance to HYDRA.
An airfield runway was soon built in the base. The parts of the Valkyrie, the gigantic super bomber whose parts were built in HYDRA's factories all over Europe, were brought to the base where the plane was finally finished.
The next day, Captain America led an attack to the facility. In a frontal assault, Rogers managed to evade and defeat many of the guards defending the perimeter and destroyed the HYDRA Mini Tank guarding its entrance. Inside the courtyard, Captain America defeated many of the soldiers guarding the base, and destroyed the front gates with an explosive carried on his own motorcycle, before being surrounded by guards carrying flamethrowers.
Rogers was taken to Schmidt's presence, who was surprised by Rogers' arrogance thinking he could attack the base alone. Schmidt asked why he was so special that Abraham Erskine gave him all that was negated to Schmidt, but Rogers humbly answered that he was not special, he was only a kid from Brooklyn.
Schmidt, infuriated, hit Rogers, who claimed he could resist all day. Schmidt, wanting to put an end to Captain America's interference in his plans, was about to shoot him when he was distracted by the Howling Commandos, who managed to infiltrate the base through the windows of Schmidt's study and attacked the guards. This distraction allowed Rogers to free himself and caused Schmidt to flee in order to fulfill his plan.
The United States Army, led by Chester Phillips, started a full-scale attack over the base killing many members of HYDRA. Meanwhile, Rogers pursued Schmidt, being blocked by another soldier carrying a flamethrower. Peggy Carter attacked the soldier and made its weapon explode, clearing Rogers' path.
Schmidt boarded the Valkyrie and started its engines to abandon the HYDRA Headquarters. Captain America tried to reach the plane, but when it appeared to be out of his range, Phillips and Carter arrived on Schmidt's personal car, to allow Rogers board the plane. Captain America managed to jump over one of the wings just when the plane was about to take off, and Phillips managed to stop the car before falling over a cliff.
The base was eventually captured, and Phillips, Carter and Jim Morita received a transmission from Rogers inside the Valkyrie, informing them of Schmidt's apparent death and the status of the plane, that headed to New York City in order to destroy it. To save countless civilian lives, Rogers decided to sink the plane in the ocean, with Carter tearfully saying goodbye before losing contact.