With the outbreak of the One Year War, a team of Zeon technical personnels of all sorts of backgrounds gather on the ship Jotunheim to form the 603 Technical Evaluation Unit, in charge of assessing various prototype weapons. Their first assignment is the testing of the Jormungand, a large and powerful long-range plasma cannon capable of taking out a battleship in single shot.

As the Earth Drop Operations begin, the 603rd is assigned to test the Hildolfr, a transformable mobile tank. The piloting task falls onto Maj. Demeziere Sonnen, a formerly respected tank trainer who is now disgraced and troubled by dope addiction from his own misery after Zeon abandoned armored vehicles in favor of mobile suits.

Upon news of a powerful new Federation mobile suit, Zeon propagandizes the Zudah, a mobile suit claimed to be superior to the Federation prototype. The 603rd is put in charge of testing the prototype with the help of a distinguished Zimmad test pilot Maj. Jean-Luc Duvall.