Fortress Maximus was hidden on Earth in order to protect the planet—it is often assumed that he was sent to prevent the potent energy within burgeoning mankind from falling into twisted hands—slumbered beneath its surface, with the assorted keys to his re-awakening scattered across the globe - the component pieces known as the O-Parts were concealed within ancient structures, the Orb of Sigma within a subterranean pyramid, and Cerebros, the power key of Maximus, within a South American temple, all presumably done with the aid of the early civilisations responsible for the constructions. At some undefined point, a group of six Autobots were sent to Earth to reactivate him, but when their ship crashed, they joined Maximus in stasis, until the emergence of Megatron and Optimus Prime's forces. His Headmaster component is known simply as The Emissary (Brave in Japan), while Cerebros is here the name of the Emissary's Headmaster (known as Plasma in Japan), the smallest component of the toy. Interestingly, rather than being portrayed as human/Nebulon-sized in the animated series, Cerebros was the size of a normal Transformer, making Brave Maximus civilizations far, far larger than his American predecessors.

Although he kept his agenda secret, Megatron had actually come to Earth in order to reactivate Fortress Maximus, and to that end, he kidnapped noted archaeologist Doctor Kenneth Onishi, who had detected energy emanations from Maximus beneath his city, and had mapped the location of the O-Parts. Kept comatose, a resistant Onishi's mind was read by Megatron in hopes of learning the location of the O-Parts, while the Autobots had a microchip gifted to Onishi's son, Koji, to guide them. The first of the O-Parts was located within the Cave of the Dragon, and a second was later found.

Some time later, when the hapless Predacon Sky-Byte held a tower of humans hostage, he was able to bluff the Autobots into suggesting their O-Parts as ransom, completely unaware as to what the components truly were. The plan resulted in failure, and soon after, the Autobots discovered Fortress Maximus's body buried beneath the city, bringing it to the surface and hiding it from their enemies. With the help of the liberated Doctor Onishi, the remaining five O-Parts were quickly recovered by the Autobots despite Predacon and Decepticon interference. United, the seven O-Parts formed a map that led to the Orb of Sigma, which then merged with the O-Parts to lead the Autobots to Cerebros. Unfortunately, the Decepticons successfully captured Cerebros, and Scourge was able to use the part of his programming that was Optimus Prime's to command him to activate Fortress Maximus. Summoning forth the city's transforming master computer, the Emissary, Cerebros became its head, then it in turn became Maximus's head, but the giant Transformer immediately began rampaging out of Scourge's control until Koji commanded it to stop, and Maximus once again disappeared beneath the Earth, leaving behind Cerebros in Decepticon hands.

It soon became apparent that, in his assignment as protector of Earth, Maximus had been harmonically keyed to obey commands from human beings, specifically pure, innocent ones such as children. With this information, Scourge used the part of his bio-signature that was human to briefly control Maximus until a mass of human children overrode his control. The Decepticons then kidnapped Koji's friend, Carl, and used him to control Maximus, but the plan failed when Scourge then turned Maximus on Galvatron (an upgraded incarnation of Megatron). With Cerebros finally in Autobot hands and the way to control Fortress Maximus fully understood, the Autobots countered an attack by the Decepticons by activating Maximus, who engaged Galvatron in battle and almost had him defeated(Fortress Maximused destroyed Galvatron's spaceship during the course of this battle which Galvatron combined with and Galvatron was thus severely damaged when Fortress Maximus obliterated the ship with his firepower), until he used his power-draining abilities to sap Maximus's strength, using it to boost his own.