In 1939, Dr. Bruce Dickson discovered Kalahia, a utopian civilization of scientists and explorers hidden on Mount Kalpurthia in Tibet. After living with the Kalahians for 3 years and learning their ability to travel through sub-dimensional space, Dickson fought the Axis Powers during World War II as the Thin Man. After the war, Thin Man found Kalahia's inhabitants slaughtered and its technology stolen by Agent Axis. Agent Axis was a super-powered Axis spy created when an Aryan supremacist, Japanese imperialist, and Italian sadist were inadvertently merged in a lightning storm. Thin Man spent decades hunting Agent Axis and finally murdered him in recent years.
Soon after, Axis Mundi-a global terrorist network composed of covert cells, dedicated to reestablishing the Third Reich-began to form. Leading members included Der Gotteskrieger, a radically religious Neo-Nazi with powers siphoned from WWII Nazi super-soldier Master Man; Warrior Woman, a man-hating Nazi empowered by a super-soldier formula of her own design; Baroness Blood, leader of the cult of day-walking, Neo-Nazi vampires known as Der Blutsauger; and U-Man, a rebel Atlantean scientist. Funded by Hydra, necromancer Professor Jonas Eckhardt resurrected the soul of Agent Axis and used it as a genetic template for the Pterorists, an armada of insect-like synthezoids that would serve as Axis Mundi's foot soldiers. Meanwhile, the Nazi war criminal Red Skull, posing as U.S. Secretary of Defense Dell Rusk, recruited Thin Man to develop a weapon to combat Axis Mundi. While Thin Man used Kalahian technology to construct the stealth battleship Infiltrator (capable of dropping entire cities into sub-dimensional space), Red Skull recruited a new unit of Invaders to serve as Axis Mundi's unwitting puppets. These Invaders included Tara, an incendiary synthezoid constructed by Axis Mundi, programmed with protocols to eliminate the team once she gained their confidence. After the Red Skull was publicly exposed, Thin Man and the new Invaders took the Infiltrator and committed themselves to stopping Axis Mundi.
Axis Mundi planned to eliminate key world leaders and replace them with bioengineered replicas. They assassinated President Hassan of the Middle Eastern Republic of Mazikhandar, and replaced him with a bio-replica, hoping to disrupt the flow of oil to the western world. This plan was foiled by the Invaders and Avengers, after which Prince Namor the Sub-Mariner named Mazikhandar a protectorate of the Atlantean throne. As Pterorist swarms invaded Mazikhandar, Der Gotteskrieger, Baroness Blood, Warrior Woman, and U-Man led a surprise attack on the Infiltrator. They were repelled by the Invaders. Professor Eckhardt was eventually captured and interrogated by the Invaders.
The Invaders later stopped U-Man from detonating a thermonuclear warhead capable of flooding the surface world, but he managed to activate Tara's protocols. As Thin Man disabled the warhead by ramming it with the Infiltrator, the android Jim Hammond sacrificed himself to absorb Tara's excess heat. With U-Man and his followers in Atlantean custody and a dysfunctional Tara in the care of the Invaders, the remaining members of Axis Mundi remain at large, undoubtedly formulating new plans to further their cause.