Jotunheim, a Principality of Zeon's space cargo ship, is tasked to test and evaluate various prototype weapons during the One Year War in the year of 0079 UC.

Universal Century 0079: The Principality of Zeon and the Earth Federation are fighting each other during the infancy of the One Year War. Zeon's Jotunheim (once a civilian space cargo ship) has been commissioned to test various weapon prototypes against the Earth Federation, in tests to be conducted by the crew of the Jotunheim, the 603 . Oliver May is the engineering lieutenant in charge of reporting the outcome of the prototype tests, to determine what weapons should be mass-manufactured for Zeon usage during the upcoming months of war. These prototype weapons include the Jormungand cannon, the Hidolfr tank, and the EMS-10 Zudah Mobile Suit. The Hidden One Year War also includes events pivotal in the Universal Century timeline, such as Operation British, the Battle of Loum, and the aftermath of Operation Odessa.