During the One Year War, Cima served as a Lieutenant Colonel in the Zeon military and as the commanding officer of a contingent of marines, all of whom were from her home colony of Mahal.
In the opening stages of the war, Supreme Commander Gihren Zabi formulated Operation British, a plan to perform a colony drop on the Earth Federation, and sent Cima and her men to clear out the population of a Side 2 colony by pumping gas into it so the colony could be dropped on the Earth Federation's Jaburo headquarters. Cima and her men were unaware that the gas they were using was a deadly nerve agent, having been told by there superior that it was knockout gas, and did not realize the truth until the G3 gas was pumped in and killed the entire population of the colony. At that point, Cima was spotted by a resident of the colony, Shiro Amada, who had survived the gassing and frantically tried to explain that it was a mistake.
Late into the war, Mahal had its civilian population evacuated by the Zeon military so it could be converted into a Colony Laser to use against the Earth Federation Forces. Because the officer in charge of the evacuation, Asakura, did not keep records of where the population was sent, Cima and her men were left without a way to reconnect with their families.
As the One Year War reached its end, Cima attempted to get revenge on her superior Asakura for tricking her into committing a war crime, but Asakura got away. To receive amnesty, Asakura pinned the gassing of Side 2 entirely on Cima and her marines, resulting in Cima and her men being barred from entering Axis like the rest of the surviving Zeon forces. With no where else to go, Cima and her fleet became space pirates in order to survive. Her experiences in the One Year War caused Cima to lose her faith in the Zeon ideal and instead develop a grudge against its surviving followers.
Later, in U.C. 0083, when Aiguille Delaz and his fleet commenced their plan to avenge Zeon's defeat by performing a colony drop on the Earth Federation, Delaz contacted Cima and her fleet to provide support for Operation Stardust. However, desiring revenge for being made a scapegoat, Cima secretly made a deal with the Earth Federation to act as a spy within the Delaz Fleet and to sabotage Operation Stardust.
While pretending to assist the Delaz Fleet, the Cima Fleet had several engagements with the crew of the Albion and the pilot of the RX-78GP01 "Zephyranthes", Kou Uraki. In one of these engagements, Cima was responsible for the death of the Albion's captain, South Burning, leading Kou to develop a grudge against her.
As the Delaz Fleet prepared the colony drop, Cima finally made her move and betrayed Aiguille Delaz, pulling a gun on him and ordering him to cancel the colony drop. However, Delaz instead ordered his second-in-command Anavel Gato to go through with Operation Stardust, resulting in an angry Cima executing him.
As Cima went out in her mobile suit to stop Gato from dropping the colony, she was confronted by the crew of the Albion, who ignored orders not to engage her and attacked her fleet to avenge South Burning. Cima went out in the AGX-04 Gerbera Tetra to defend her fleet from Kou in the RX-78GP03 Gundam "Dendobrium". Despite Cima's combat experience and the agility of the Gerbera Tetra, she was unable to match up to the GP03's superior technology and was killed by the mega beam cannon of the GP03.