HYDRA

"Hail, HYDRA! Immortal HYDRA! We shall never be destroyed! Cut off a limb, and two more shall take its place! We serve none but the Master—as the world shall soon serve us! Hail HYDRA!"

- The HYDRA Oath

HYDRA is a terrorist-military organization bent on world domination. It was founded shortly after the rise of Nazism in Germany by Johann Schmidt as the scientific branch of the Nazi Schutzstaffel. Its main purpose was to create advanced weaponry for the German armies, but over the years, members of HYDRA became loyal only to Schmidt himself. In 1943, Schmidt separated HYDRA from Nazi Germany to start his own conquest of the world.

After its defeat at the hands of Captain America in 1945 and the subsequent disappearance of Johann Schmidt, HYDRA was secretly rebuilt inside S.H.I.E.L.D. by Schmidt's top scientist Arnim Zola who was recruited into the agency during Operation Paperclip. After Zola's death in 1972, HYDRA was taken over by Baron von Strucker who continued to lead the organization into the 21st century. Under his leadership, the agents of HYDRA managed to infiltrate many important organizations, including the United States Senate.

Foundation and first actions
""Howard, the footage you're about the see was just smuggled out of Nazi Germany by "Agent 13", an undercover operative the British have planted deep within HYDRA, Hitler's advanced weapons program.""

- Chester Philips

HYDRA has its roots in the special weapons division of the Nazi Sturmabteilung. Led by Ernst Kaufmann, the division was charged with developing advanced weapons for the German army. In June 1934, during the Night of the Long Knives, Kaufmann was killed by the SS officer Johann Schmidt. Schmidt and his men eliminated Kaufmann's entire unit, except one man, Dr. Arnim Zola. Schmidt took over Kaufmann's weapons program and formed his own SS division, naming it HYDRA. HYDRA was named after the mythological creature and used its original phrase: "cut off one head, two more will take its place". It was soon charged with science experiments and deep investigation of the occult. Due to contributions from Arnim Zola, HYDRA developed several extremely advanced weapons. When the Spanish Civil War started in 1936, the leaders of the Third Reich decided to support the Nationalists led by Generalissimo Franco. HYDRA was among the German units sent by Adolf Hitler to assist the Nationalists on the battlefield. In April 1937, HYDRA's armored vehicles and soldiers equipped with powerful exo-skeleton battle suits destroyed the city of Guernica. At the time, it was believed the German air force, the Luftwaffe, was responsible for the destruction of the city. However, the footage of the slaughter was smuggled out of Germany by the British agent Margaret Carter and handed over to the US military in January 1940.

Marvel Cinematic Universe
HYDRA appeared as the main group of villains in the movie Captain America: The First Avenger, and were led by Johann Schmidt, the Red Skull. They were stated as being part of the Nazi's deep science division, and they had tech that was superior to anything created at that time. Most of their tech was powered by the Cosmic Cube. Eventually Red Skull revealed plans to bomb various cities in the world, including Berlin. As such in the movie HYDRA has broken of from the Nazi Party and seek to replace them.

HYDRA returns in Captain America: The Winter Soldier with Alexander Pierce as their new leader. They plan to launch Project Insight which was thought to be done by SHIELD as a security enhanced project. But it was revealed by the consciousness of Arnim Zola through a supercomputer that HYDRA infiltrated SHIELD and that Project Insight is all a HYDRA plan to launch the three SHIELD Helicarriers and target over a million lives according to a special algorithm that Zola developed for HYDRA to follow. HYDRA is also revealed to have found Bucky in between films and brainwashed him to becoming the Winter Soldier. At the end of the film HYDRA is now lead by Baron Von Strucker and have captured Quicksilver and Scarlet Witch.

The events of Captain America: The Winter Soldier crossed over into the ABC TV series, Marvel's Agent's of SHIELD. The Clairvoyant who was actually a SHIELD agent named John Garrett who had level 7 clearence was assisting Alexander Pierce in the infiltatuon of SHIELD. He betrayed Agent Phil Coulson, who was a friend of his and he somehow got Grant Ward who was in Coulson's team as a HYDRA. He implicated Victoria Hand, another high level SHIELD agent as an agent. John also had his own organization known as the Centipede Group working for him. They assisted him and HYDRA on various occasions. Despite the fact he was captured, HYDRA ulimately succeeded in taking down SHIELD and escaped, thanks to Ward killing some loyal SHIELD agents, including Victoria Hand, while transporting Garrett to a SHIELD prision facility.

Varioius

 * Baron Von Strucker (Supreme Hydra)
 * Red Skull
 * Baron Zemo
 * Baron Zemo II
 * Viper (Madame Hydra)
 * Arnim Zola
 * Kingpin
 * Kraken
 * Grim Reaper
 * Silver Fox
 * Fixer
 * Silvermane
 * Richard Fisk
 * Silver Samurai
 * Gorgon
 * Crossbones
 * A.I.M.

Marvel Cinematic Universe

 * Alexander Pierce
 * John Garrett (Clairboyant)
 * Grant Ward (suspected member)
 * Centipede Group
 * Raina

Amalgam version

 * Green Skull (Leader)
 * Baron Zero
 * Madame Cat
 * Nuke
 * Ultra-Metallo
 * Major Zemo

Trivia

 * HYDRA's abandonment of the Nazi cause is more elaborated in a deleted scene from Captain America: The First Avenger where a HYDRA Tank fires at regular German troops before it captures the future Howling Commandos. However, that scene contradicts the events of Captain America: First Vengeance, Volume 6 where HYDRA still works for the Nazis after the imprisonment of the Howling Commandos.
 * In the Marvel Comics, HYDRA was organized by Baron Wolfgang von Strucker in the Japanese-occupied territory in the final days of World War II.
 * HYDRA appears briefly in X2: X-Men United and X-Men: The Official Game.
 * In the animated series of The Avengers: Earth's Mightiest Heroes, HYDRA was led by Baron Zemo during World War II. After the war, Baron Wolfgang von Strucker took command of the organization.