In 1869, Abraham Erskine is born in Augsburg, Germany. Abraham Erskine, working in a German University, begins his research into creating a Super Soldier Serum.
In Hell's Kitchen, New York City, a young Steve Rogers meets Bucky Barnes, who ends up becoming his best friend.
Johann Schmidt begins searching for the Tesseract.
At the Deutsches Opernhaus in Berlin, Johann Schmidt meets Adolf Hitler and Ernst Kaufmann head of the Special Weapon Division after the performance of a Wagner opera. Schmidt reveals his theory that the Asgardians and their magic could be more than a myth. Hitler is intrigued by his ideas, and Schmidt offers to conduct research in Kaufmann’s unit, but is rejected. Heinrich Himmler overhears the conversation and takes Schmidt under his wing.
At the Schutzstaffel's Night of the Long Knives, Johann Schmidt kills Ernst Kaufmann and seizes control of his weapons program. Johann Schmidt and the SS troops attack an SA Weapons Testing Ground at Kummersdorf, and recruit advanced exo-skeleton battle armor researcher Arnim Zola.
World War II begins. Howard Star founds Stark Industries.
In Los Angeles, California, Howard Stark demonstrates the properties of Vibranium, a metal found by Stark Industries in Africa. Stark is attacked by HYDRA assassins. Then, Stark accepts Colonel Chester Phillips' proposal to join the Strategic Scientific Reserve.
At Castle Kaufmann in the Bavarian Alps, Abraham Erskine injects Johann Schmidt with his Super Soldier Serum, but the serum horrifically transforms Schmidt, turning him into the Red Skull.
Abraham Erskine is rescued by Peggy Carter, who had infiltrated the compound disguised as a maid. Carter takes Erskine to the Strategic Scientific Reserve (SSR) so he can produce America's Super Soldier with the aid of Howard Stark.
Bucky Barnes and Steve Rogers enlist while visiting New York City’s U.S. Recruiting and Induction Center, but Steve is designated 4F and rejected. He tries four more times in four different cities but meets the same fate each time.
In Tønsberg, Norway, Johann Schmidt (Red Skull) discovers and takes the Tesseract, hidden within a monastery. He refers to it as "the jewel of Odin's Treasure Room".
HYDRA General Warner Reinhardt’s team, tasked with discovering more artifacts related to the Tesseract, find the corpse of a blue-skinned extraterrestrial, a Kree soldier they dub G.H.
Steve Rogers is recruited by Dr. Erskine for Project Rebirth. Steve Rogers is successfully transformed through the use of the super-soldier serum. However, Dr. Erskine is assassinated by HYDRA operative, Heinz Kruger. The only hope of replicating Project Rebirth's success is in Rogers' genetic code. Kruger runs away but is caught by Rogers and commits suicide with a cyanide pill.
Battle of Azzano: The 107th Infantry Regiment suffers heavy casualties fighting against the German Army and HYDRA. HYDRA openly fires at German troops, breaking ties with Nazi Germany
Steve Rogers refuses to be kept in a lab as a research specimen and goes on a USO tour instead as Captain America. Captain America leads an assault on a HYDRA facility in Austria to liberate Dum Dum Dugan, Gabe Jones, Jim Morita, James Montgomery Falsworth, Jacques Dernier, Bucky, and the rest of the 107th, some of whom will form the Howling Commandos.
Johann Schmidt sets the facility to self destruct and escapes with the Tesseract. During his escape Rogers memorizes a map of HYDRA facility locations and obtains a sample of the power source HYDRA was using. Howard Stark examines a sample of HYDRA's power, which will help him develop a framework to synthesize a new element.
Capture of Arnim Zola: The Howling Commandos board a HYDRA train and capture Arnim Zola. In the ensuing battle with HYDRA agents, Bucky Barnes falls from the train and is presumed dead.
Two months later, Captain America defeats Red Skull, but in order to prevent Red Skull’s bomber from attacking the United States, he is forced to crash the plane somewhere near Greenland. He is lost and presumed dead.
As Red Skull escapes in the Valkyrie, Captain America gains access to the plane and a fight ensues. Red Skull handles the Tesseract, which activates and sends him through a portal to the planet Vormir. There, he is stranded for over 70 years and tasked with guarding the Soul Stone until 2018.
World War II ends. Howard Stark recovers the Tesseract during his search for Captain America, and it eventually becomes top secret S.H.I.E.L.D. property.
After the war, Peggy Carter and Howard Stark become two of the founding members of S.H.I.E.L.D. Stark also turns his company Stark Industries into one of the largest munitions and military contracting companies in the world.
Arnim Zola is released from prison as part of project paperclip and joins S.H.I.E.L.D., but secretly enacts a plan to rebuild HYDRA within it. He recruits sleeper agents and spreads them throughout the agency and the U.S. government.
HYDRA recovers Bucky Barnes, who survived his presumed death. Bucky is brainwashed to become an assassin known as the Winter Soldier. The procedure removes his memories of his past life and identity, and when he’s not on mission, Bucky is frozen in cyrostasis, keeping him in peak physical condition for decades.
The Winter Soldier is used for covert HYDRA missions, including the assassination of President John F. Kennedy. Hydra operatives work behind the scenes to sow chaos worldwide as part of a plan to eventually create a fearful population desperate for security.
Young Natasha Romanoff is recruited into a ruthless KGB assassin program. This continues after the dissolution of the USSR and she becomes one of Russia’s top assassins, code-named Black Widow.
S.H.I.E.L.D. Agent Clint "Hawkeye" Barton is sent to kill Natasha Romanoff , but convinces her to defect to S.H.I.E.L.D. instead.
Captain America is discovered frozen, but still alive thanks to the super-soldier serum. S.H.I.E.L.D. revives Rogers, who discovers that he has been asleep for 66 years.
Arnim Zola and his hidden HYDRA sleeper agents in S.H.I.E.L.D. and the Government finally enact their plan to openly take over the world using S.H.I.E.L.D. technology to eliminate anyone who might be a threat. Nick Fury is apparently killed during the takeover, but it turns out he’d been anticipating something like this and faked his own death.
Teaming up with Black Widow and his new friend Sam “Falcon” Wilson, Captain America uncovers the plan, and is forced to fight The Winter Soldier, whom he discovers is his old friend, Bucky. With the help of Fury and S.H.I.E.L.D. agent Maria Hill, they’re able to defeat HYDRA.
During the battle, Bucky regains some of his memories and goes on the run as a fugitive. After ward, Maria goes to work for Stark Industries, Cap and Falcon begin a worldwide search to find Bucky, Fury (still believed dead) heads to Europe to root out hidden HYDRA cells, and Black Widow releases all of S.H.I.E.L.D. and HYDRA’s secrets
to the public.
HYDRA boss Baron von Strucker conducts experiments on Sokovian siblings Wanda and Pietro Maximoff using Loki’s Scepter (Mind Stone) giving them superpowers.