The History of the MCU’s Super-Soldier Serum

In the Marvel Cinematic Universe, many characters we know and love all have a shared connection through the Super-Serum Project. First mentioned in 2008’s The Incredible Hulk, the Super Soldier Serum was a formula created many times throughout history to create super-soldiers, soldiers with enhanced strength and agility. From the 1940s through to 2023, the serum was responsible for key events throughout the MCU, ensuring battles were won & significantly shaping society as we know it. 

Erskine Formula

The original serum was developed by Dr. Abraham Erskine in 1930s Germany. By 1940, Erskine was forced to test his prototype serum on Johann Schmidt – leader of the Nazis’ HYDRA division. The process successfully gave Schmidt the enhanced strength he had asked for, but with severe side-effects including hair loss/red skin and a skeletal-looking face, providing him with the name, Red Skull.

Erskine escaped to America and helped the Allied SSR (Strategic Scientific Reserve) create more super-soldiers to fight back against the Nazi menace. Erskine improved upon his formula, realizing that Vita-Ray radiation would be the key to a successful transformation and understanding that choosing the perfect candidate was equally important. Johann Schmidt was evil before injecting himself with the serum but his personality had worsened after taking it, leaving Erskine to surmise that the effects depends on the persons’ heart.

After observing Steve Rogers attempting to join the Army at the Stark Expo enlistment booth, Erskine interviewed him regarding his reasons for wanting to join the fray. Comfortable with his answer, and after significant training under the SSR, Steve was injected with several vials of the serum and subjected to vita-rays – causing visible distress to Rogers, yet telling them to keep going regardless. After the process was completed, the once-scrawny-Brooklyn kid emerged as a taller, stronger soldier.

Steve Rogers was officially the first successful trial subject for the Super-Soldier serum. Sadly, a HYDRA spy was infiltrating during the experiment and murdered Dr. Erskine. In the resulting chase, the remaining vials of the serum were destroyed, its secret formula having died alongside the man who created it. A disaster for the US and the Allied Forces, the project titled “Rebirth” or “Weapon Plus” was put on hold. Blood samples were taken by Rogers in an attempt to recreate the formula, but to no avail, leaving Captain America and the Red Skull as the only super-soldiers at that time.

HYDRA also attempted to recreate their own super-soldier serum during the war, experimenting on prisoners of war – such as James Buchanan Barnes (Bucky) in 1943. HYDRA’s original research attempts by Dr. Arnim Zola were halted when Captain America and the Howling Commandos freed the prisoners and escaped with Bucky, who at first didn’t seem to have side-effects or visual effects of the serum had worked. It wasn’t until after his traumatic fall during a mission in 1945 in which he lost an arm, yet survived, that the effects of the serum started to kick in. Bucky was then taken in by the Soviet Union and given to their HYDRA division as a prisoner of war. With Captain America encased in ice and the Red Skull sent to the planet Vormir, Dr. Zola began creating the Winter Soldier program, brainwashing Bucky Barnes and turning him into a weapon.

Isaiah Bradley & The Cold War

HYDRA, embedded throughout SHIELD, used the Winter Soldier as a weapon to help solidify their placement in different governments and power bases throughout the world. During this time, The US Military attempted to recreate the super-soldier serum, recruiting a dozen Black soldiers against their will and consent, under the false pretense of a tetanus shot. These soldiers were then sent out to fight in the Korean War, many dying from the serum they were forced to take. One soldier, Isaiah Bradley was sent on a mission to kill the Winter Soldier in Goyang, severely besting the brainwashed Bucky and ripping his arm out of his socket causing him to retreat. Because he was the closest to killing the Winter Soldier, he was considered a major threat by HYDRA – on the same level or above Steve Rogers.

When he found out that his fellow soldiers had been captured as prisoners of war and that the US was going to bomb the compound to cover up their experiments on these men, Isaiah bravely fought through enemy lines and rescued them and 28 other POW’s. However, Isaiah was arrested and imprisoned alongside his fellow soldiers, who were killed while in prison. The US then covered up any existence of Isaiah’s bravery and exploits, effectively erasing him from history – fearing that his story would inspire Black citizens throughout America. Both the CIA and HYDRA would routinely, and forcefully take blood samples from Isaiah for 30 years, trying to determine why the serum succeeded in this case.

The Winter Soldier continued working for HYDRA, shaping the world in their image by taking out threats such as John F. Kennedy and in 1991; Howard and Maria Stark. During that year, Howard Stark had successfully recreated his own version of the super serum, which was highly sought after by HYDRA. Defrosting and activating their assassin, the Winter Soldier was sent to murder his once friend Howard and his wife Maria, and to take the new case of serum back to his handlers. Succeeding in his mission, HYDRA utilized this formula to create even more Winter Soldiers, without the use or need of vita-rays.

While this serum produced stronger soldiers, it also had the side-effects of extra-aggression, causing these Winter Soldiers to fight back against their HYDRA handlers. After subdued by the Winter Soldier and other HYDRA agents, these subjects were put back on the ice until a successful way of controlling them could be established. This would never happen, as the facility was shut down later that year when the Soviet Union collapsed, and these soldiers would be forgotten.

The Banner Formula

After the attacks on September 11, 2001, General Thaddeus Ross attempted to, once again, recreate the super-soldier serum for the US Armed Forces. He would later hire Dr. Bruce Banner, an expert in gamma radiation, for the project – lying under the pretense that they were attempting to find a cure for radiation poisoning.

Banner came to the conclusion that the original use of vita-ray radiation could be replaced by gamma radiation. By 2005, he began testing the replicated formula on himself and then used gamma rays to produce a similar outcome to Steve Rogers – but instead was transformed into the Hulk. The project, known as Bio-Tech Force Enhancement, was put on hold, although some vials of the replicated formula were kept alongside vials of Dr. Banner’s radiated blood.

In 2010, this serum was once again used by General Ross, giving it to Emil Blonsky while they tracked down The Hulk. Unfortunately, Blonsky began to grow erratic after his first dose and physically change during his second, forcing Samuel Sterns to inject him with vials of Dr. Banner’s irradiated blood, turning him into the Abomination.

During this time, HYDRA tasked Dr. Nagel with recreating the super-soldier serum after their use of Howard Stark’s recreation ended in disaster. For many years, he worked for HYDRA with seemingly no progress, until the organization was disbanded in 2014. Two years later, Baron Zemo found the missing Winter Soldiers from the 1990s and murdered them all, believing that super-soldiers were inherently dangerous and on a path to supremacy. With this act, Howard Stark’s serum was effectively erased.

Final Serum

After HYDRA dissolved, the CIA picked up Dr. Nagel and his research with the intent of making their own super-soldiers. Using the blood samples that were forcibly taken from Isaiah Bradley, Nagel was finally able to devise a way to replicate a working version of the super-soldier serum that would not need vita rays, nor would physically change the recipient. However, before he could synthesize his hypothesis, Thanos’ snap turned Dr. Nagel and 50% of the population to dust.

After The Hulk brought back everyone who had been blipped in 2023, Dr. Nagel’s research had been shut down by the CIA, forcing him to retreat to Madripoor. It was here that Sharon Carter, the Power Broker, gave him the resources to finally create his life’s work; 20 vials of the new serum. These vials were stolen by Karli Morganthau, the leader of the Flag Smashers, a group attempting to create a world without borders. The group used some of the vials, making themselves super-soldiers and attempting to later use the rest to create more for their cause.

Dr. Nagel was once again trying to replicate the formula when he was murdered by Baron Zemo. His research was subsequently destroyed in the following assault from assassins in Madripoor. Zemo would later destroy the remaining vials of the serum in Karli’s possession, bar one, which was used by John Walker, the then-current Captain America. Walker’s already fluctuating temperament, probably caused by PTSD, was worsened by his use of the serum, echoing the theory that Erskine came up with so many years ago.

In a final battle, Karli was killed by Sharon Carter in an effort to conceal her identity as the Power Broker and responsibility in empowering both the Flag Smashers and Walker. The other Flag Smashers were then murdered under the orders of Baron Zemo from his cell, almost completing his aim of wiping out those he believed were a threat to the world. By the end of Falcon and the Winter Soldier, there are only three* remaining super-soldiers: Bucky Barnes, Isaiah Bradley and John Walker.

Throughout the history of the MCU, the super-soldier serum has created both good and terrifying pain for millions of people throughout the centuries. Much like Dr. Erskine stated right at the beginning, the serum amplifies what’s already in the person who takes it. It’s just unfortunate, many of those behind these projects, such as HYDRA and the US Government have operated with cruel intentions. With John Walker becoming the US Agent and Elijah Bradley being established in the MCU, it’s unclear whether we’ll truly see “the end” of the super-soldier serum, but for now, it’s a project best left in the past.

*Technically, Bruce Banner could classify as surviving member of someone who took the serum. But it’s unclear whether he should be classified as a super-soldier. We don’t actually know whether Steve Rogers is alive or dead, so for now, let’s put that down as a maybe.