Days after the Tet Offensive in Vietnam, General Demetrius Lazer visits the Xavier Institute with startling news. The United States had a covert all-mutant team called “Weapon X.” During the offensive, the Chinese revealed that they had their own all-mutant team, called the People’s Defense Force. They worked alongside a Viet Cong mutant and a Soviet mutant to seize Weapon X’s base of operations and take the mutants involved prisoner. With the army occupied with responding to the Tet Offensive, the General must turn to the X-Men to rescue the mutant POWs.
From Saigon, Cyclops, Nightcrawler, Iceman, and Jean Grey trek across enemy-infested jungle with a platoon of U.S. marines led by Lieutenant Frank Castle to retake Firebase Valley Forge, where Weapon X had been operating. The base revealed the extent of Weapon X’s experimentation on mutants, including bonding their skeletons with adamantium in a process that would kill anyone without their mutant healing factor, and telepathic conditioning and brainwashing.
Soon after they faced the People’s Defense Force: Collective Man, the Radioactive Man, the Lady of the Ten Suns, and Scientific Beast. They agree to work together to find John Wraith, a teleporter with Weapon X who avoided capture. When they catch up with him, the People’s Defense Force begins attacking Wraith, so the X-Men turn on them to defend him. The battle goes poorly for them until the Mutant Brotherhood intervenes. They say they’re going to rescue their mutant brethren from captivity, and invite any of them to join them.