Super Soldier Serum

"His serum is the Allies' only defense against this power we now possess."

- Johann Schmidt to Arnim Zola

The Super Soldier Serum is a chemical solution originally created and developed by Abraham Erskine. The serum was formulated to enhance the human body and mind, and was intended to be utilized by the United States Armed Forces during World War II in order to transform Allied soldiers into super soldiers.

Over the decades, it has been recreated by several parties, most with a considerable degree of success. It is notably responsible for the superhuman abilities of Johann Schmidt, Steve Rogers, James Barnes, Milly Taylor, Emma Taylor, Bruce Banner, and Emil Blonsky, as well as other individuals converted into super soldiers by a joint Soviet-HYDRA operation.

Prelude
"The compound is part of a formula that first appeared in Germany during World War II."

- Jemma Simmons Abraham Erskine began developing the Super Soldier Serum in 1930 while still in Germany. In 1931, Wilfred Malick brought one of the key ingredients of the formula to HYDRA with the assistance of Viola.

World War II
"My serum did not fail. It did... exactly what I designed it to do. It enhances what is already within. It is Herr Schmidt... who has failed... at being human."

- Abraham Erskine to Arnim Zola

Ten years later, in 1940, the Super Soldier Serum was tested on Johann Schmidt, turning him into Red Skull in the process. However, the formula wasn't ready for use at the time, and the serum's effects affected Schmidt's personality drastically. Schmidt's transformation didn't go as planned because his Super Soldier Serum lacked radioactive exposure, causing the burning away of the skin and tissue surrounding his skull as well as leaving an unpleasant red scab on his nasal cavity.

After Abraham Erskine escaped to the United States of America, he joined the Strategic Scientific Reserve and took part in Project Rebirth, a project to create a Super Soldier for the Allied forces. Using Vita Radiation to unlock the serum's potential, Erskine successfully used the serum on Steve Rogers. Unfortunately, Erskine was killed and the last vial of the original serum was destroyed by Heinz Kruger, with the last remnants of the serum remaining in Rogers' DNA.

In October 1943, HYDRA captured numerous US military soldiers, including Bucky Barnes, and sent them to work at the top-secret weapons facility in the Austrian Alps. When he was too weak to work, Arnim Zola used him as a subject for his experiments with his own version of the Super Soldier Serum. Barnes was injected with the serum shortly before the prisoners were liberated by Rogers a month later.

During the first icy months of 1945, Rogers and Barnes led an attack on the HYDRA train that was transporting Zola to another base. During the fight, Barnes fell from the train, falling into an icy river below, whose cold waters no ordinary man could survive. However, thanks to the serum's effect on his body, Barnes was able to survive, though at the cost of his left arm.

Winter Soldier Program
"The most elite death squad. More kills than anyone in HYDRA history. And that was before the serum." "They all turn out like you?" "Worse."

- Bucky Barnes and Sam Wilson

In December 1991, HYDRA learned that Howard Stark had recreated the serum and dispatched Bucky Barnes, who had been turned into the Winter Soldier, to retrieve it. Upon the assassination of Howard and Maria Stark, Barnes retrieved the case containing five I.V. bags of the serum, which HYDRA used to create a team of superhuman assassins. This serum caused an excruciating transformation without the need of Vita Rays, which afterward left the subject physically more superhumanly 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 Winter Soldiers. However, these soldiers were not as easily controlled at first, due to the mental side effect of this variant of the serum, giving them an increase in aggression. Once one of the subjects succumbed to the enhanced aggression, soon all of the Winter Soldiers, aside from Barnes, where shown to suddenly turn on HYDRA Soldiers that handled them in one instance. However, they were soon brainwashed like Barnes and placed in suspended animation.

United States Armed Forces
"You're aware that we've got an Infantry Weapons Development program. Well, in WWII, they initiated a subprogram for Bio-Tech Force Enhancement." "Yeah. Super Soldier."

- Thaddeus Ross and Emil Blonsky

In 2001, the United States Armed Forces revived the Bio-Tech Force Enhancement Project, a secret project set-up after the relative failure of Project Rebirth, under Thaddeus Ross' command. A failed attempt to reproduce the serum with added bouts of Gamma Radiation led to the accident that turned Bruce Banner into Hulk. Banner was later forced to flee from Ross, who employed Emil Blonsky to track him down. Later to sustain Blonsky's will to fight, Ross gave him an injection of a variant of the serum, which gave him abilities similar to those of Captain America. Later combination with the altered serum in Banner's blood turned Blonsky into the Abomination.

Centipede Project
"This goo, sir. Very similar to the serum Dr. Erskine developed in the 40s for the–" "Super soldiers."

- Jemma Simmons and Phil Coulson As of 2013, HYDRA started the Centipede Project, as their scientists managed to recreate a very similar version of the Super Soldier Serum as one of the components of the Centipede Serum, designed to give a person superhuman abilities. This serum was mixed with the Extremis, Gamma Radiation and the Chitauri technology for injection.

Capabilities
"The serum amplifies everything that is inside, so good becomes great, bad becomes worse."

- Abraham Erskine to Steve Rogers

The raw serum's general properties seemed to be enhanced and perfected physiology and mentality, as well as emphasizing the user's key personality traits. The version of the serum given to Bucky Barnes, however, did not seem to enhance any of his personality traits and only augmented his physicality.

When saturated with Vita Radiation, the serum worked more successfully by stimulating growth in the body. Gamma Radiation was believed by Bruce Banner to work similarly, but instead corrupted the serum's effects, making it unstable, and turned him into the raging monster known as Hulk. However, replicated versions of the serum, such as the one used on Emil Blonsky, did not need the radiation for changes to happen, although they happened more gradually.

The normal effects of the serum are an increase in the molecular density of cellular fibers (skin and muscle) through synthetic proteins. This means that the serum can naturally enhance the proteins inside the subject, as well as their effects, effectively granting the subject enhanced physical abilities.

It also naturally enhances metabolic, cellular, and chemical processes in the body, which can enhance recovery and healing abilities, as well as building up greater resistance to fatigue and exhaustion. These can also allow a subject to fully recover without drugs, medicines, or other medical or therapeutic treatments. In addition, the serum may also affect the subject's dopamine, testosterone, adrenaline, various other endorphins, and hormones, enhancing the effects of such chemicals to further amplify the subject's physical and even mental performance.

However, Blonsky's healing and regeneration capabilities appear to be far more accelerated compared to other super-soldiers, as he could completely heal and recover from every bone in his body being destroyed and being left crippled into a near death-like state, within a few hours. Steve Rogers on the other hand, took at least a day or more to heal from small ballistic wounds. Blonsky's accelerated healing and regeneration are due to his having a different version of the serum infused into him. In addition to all super-soldiers' healing capabilities, the Super-Soldier Serum has its limitations as individuals like the Winter Soldiers were unable to heal from getting shot in the head with a bullet by Helmut Zemo.

Another example would be that the Winter Soldier's variant makes him much more durable than most of the other super-soldiers, enough to survive a fall from the Swiss Alps.

The serum used in the Winter Soldier Program that was procured from Howard Stark by Winter Soldier, caused an excruciating transformation without the need of Vita Rays, much like the serum used on Blonsky, 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 superhuman. However, these soldiers suffered mental side effects, as they were shown to suddenly turn on and kill the HYDRA Soldiers that handled them in one instance. However, they were eventually placed in suspended animation until they were found and killed by Helmut Zemo.
 * Johann Schmidt was the first user of the serum, a prototype version that had yet to be perfected. According to Abraham Erskine, neither he nor the serum was ready, and while Schmidt gained enhanced abilities, the skin of his face had burned off.
 * Steve Rogers was the first and only recipient of the perfected serum. The serum granted him superhuman abilities, cured him of all his medical ailments, and significantly increased his height and physicality.
 * Bucky Barnes was a second successful attempt at a super soldier, injected with serum similar to Rogers' while he was a prisoner of HYDRA in 1943. The serum enabled him to survive the fall from the HYDRA train in 1945, but was not potent enough to prevent the loss of his left arm. Afterward, due to further HYDRA experimentation, he developed physical abilities that rivaled Captain America's.
 * Josef and four other Winter Soldiers were converted into super-soldiers using a serum developed by Howard Stark. Despite being created to share the role and title of the Winter Soldier and being shown to be strong enough to relatively quickly overpower the original, despite his metal arm, they were not as versatile or useful as Barnes, who was the first and true Winter Soldier. This was due to this serum's mental side effects, including increased aggression. In one instance, they even attacked HYDRA soldiers that handled them. Because of this, HYDRA continued to use only Barnes as their assassin while cryogenically freezing the rest.
 * Milly Taylor was accidentally merged with the serum when hers and Howard Stark's lab was blown up by the Winter Soldier. Taylor, still inside, survived by the serum merging itself with her due to the radition also within the lab. Taylor received enhanced strength, but because of the incomplection, her longevity reached beyond natural years, causing her to go into hiding.
 * Emma Taylor is the daughter of Milly Taylor and Howard Stark. She was a fetus when her mother was affected by the serum, and bore similar effects such as the longevity and strength.
 * Bruce Banner attempted to recreate Erskine's original serum but replaced the original formula's Vita Radiation with Gamma Radiation before administering it on himself. The different radiation prompted him to turn him into an aggressive muscular, giant humanoid version of himself with green skin. Banner reverted to his original state but would transform again in the future whenever his heart rate became too high or he became extremely angry and lost emotional control. This is due to the gamma in his body being stored in his cells and being reactivated due to emotional or physical stress. Banner had a limited ability to control his transformations by remaining angry at all times without releasing his anger to keep him from transforming. When he is transformed in this controlled manner, Hulk is not mindless, as he would be if Banner did not willingly transform. However, over time, Hulk gained more and more of its own mind, to the point where he could take control of the transformation process and keep himself from reverting back into Banner, as well as keeping Banner from transforming into him. Eventually, Banner spent eighteen months in a gamma laboratory to permanently transform into Hulk while retaining his personality, effectively possessing both brain and brawn.
 * Emil Blonsky had a variant of the serum injected into his spine's bone marrow and deep muscle systems, which enhanced him physically to superhuman levels. His regenerative abilities, compared to the other super-soldiers, were more advanced, to the point where he could completely regenerate from all his bones being broken or shattered all within a matter of hours. However, this serum had delayed side effects, which soon manifested as physical deformations, such as a protruding skeletal structure, as well as mental side effects, including increased aggression. After Blonsky was injected with Banner's gamma-irradiated blood, the serum kicked into overdrive, transforming Blonsky into a Hulk-sized version of himself with an external bone structure. Unlike Banner, however, Blonsky retained full control over his transformed state.

Trivia

 * Stark Industries created the injection tube that administered the Super Soldier Serum into Steve Rogers.
 * In Christopher Markus and Stephen McFeely's first draft of the Captain America script, the flashbacks would have revealed that Johann Schmidt injected himself with Abraham Erskine's serum in 1938 in Berlin, and that Heinz Kruger was one of the Nazi agents present.