With the outbreak of the One Year War, the Principality of Zeon forms the 603rd Technical Evaluation Unit, a team of soldiers, technicians, and engineering specialists in charge of assessing various prototype weapons aboard the Jotunheim, a civilian cargo ship refitted and enlisted for military use. Their first assignment is to test the Jormungand, a powerful long-range plasma cannon capable of taking out a battleship in a single shot. However, the weapon's maiden appearance at the Battle of Loum becomes its last, as a new member of the Zeon arsenal soon arrives to prove the Jormungand obsolete...