The War of Planet Arlia is the name commonly given of the war waged between the people of The Kingdom of Arlia and the evil Empire of King Moai.
The history of this war is only briefly described by Atla when Vegeta and Nappa arrive in their dungeon cells after being taken as prisoners. As Atla described, Arlia was once a peaceful planet, but one day the Kingdom of Arlia was invaded by rogue Arlians (identified from a normal Arlian by their red eyes as opposed to the regular green eyes), who were banished from the Kingdom of Arlia by Atla (Atla was the King of Arlia at the time) for their wicked crimes. These rogue Arlians, led by the Evil King Moai, attacked the Kingdom and proceeded to attack the half which was in Atla's possession. The Arlians who served Atla were defeated (it's not explained how) in one day. King Moai then took Atla's wife Queen Lemlia (who, according to Atla, married him on the very day the war broke out, only for her to be stolen from him by Moai hours later) and locked Atla's Arlians in dungeons. Moai built a colosseum around his castle, where he sent his own men to fight each other, sending the losers down through a pit in his throne room (hidden underneath a trap door which would open when a button was pressed by his Arlian) to be eaten by his pet monster Yetti. Two of his warriors were seen engaged in combat, named Greger and Lesoy and after Greger lost, he was fed to Yetti on Moai's orders. Atla's Arlians could have possibly participated in similar combats. For how long Moai ruled is unknown. However, it ended when the two Saiyans, after hearing Atla's story, released the prisoners and killed all of Moai's guards (including Lesoy) as well as his pet monster, Yetti, and Moai himself. However, this was probably just a "small exercise" to Nappa and Vegeta. The released Atla thanked them for saving their planet, promising for them to be remembered as great heroes, and decided to gather up the rest of the Arlians and rebuild the planet just like it once was. Atla then reunited with his love, Lemlia. This reunion was short-lived, however. Vegeta, evaluating that no one would buy Planet Arlia, decided to destroy it and blew up the planet, much to his and Nappa's amusement.