Ajax was a member of the Gorilla Guard that served as Luca’s second-in-command of the Guard. When a human warship arrived and open fire on the apes on the bridge, Ajax fired a rocket launcher at the ship, forcing the humans to retreat. Ajax was hailed as a hero by the other apes, despite the deaths of six apes during the fighting.
Ajax was tasked with keeping the female and children apes while Caesar's Army fought Colonel McCullough's forces inside an abandoned building. When the humans set the building next door ablaze, worked to protect the other apes from the smoke and flames. Ajax later moved with the rest of the group to woods stood together with Luca and Red, another member of the Guard, as they crowded around gorilla named Winter to hide his white fur.
After they reached the woods, Luca left Ajax in charge of the group as they continued their journey. Ajax tried to convince Cornelia to ride one of the horses because she was sick not too long ago, but she refused claiming to be fine now. Ajax offered to have the gorillas carry her and Cornelia once again refused, displeasing Ajax. Ajax awoke to find a group of gorillas and chimps trying to disarm the other members of the Guard and fought back along with another gorilla named Ursus. Ajax was wounded and managed to escape while Ursus was killed in the fight.
Ajax fled back to the old ape village with two chimpanzees, Flint and Shell, pursing him. The two chimps attacked him and Ajax smashed Flint’s skull near the entrance of the village and before he died of his wounds he plunged a spear into Shell’s chest, killing him.