The conflict started on the Transformers home planet of Cybertron. Megatron, the leader of the Decepticons, started a war with Sentinel Prime, the leader of the Autobots. During the war on Cybertron, Sentinel was lost in deep space and was replaced as Autobot leader by Optimus Prime, his second-in-command.
Cybertron was later drained of its energy and the Decepticons went looking for a new source of Energon, which fuels the Transformers and their machinery. Megatron had conspired with the Autobot leader Sentinel Prime to invade Earth long ago, but that plan was lost with Sentinel when he fled Cybertron. Instead, Megatron came to Earth looking for the Allspark, by the command of his master, the Fallen, who was an ancient Transformer (an ex-Prime, in fact) who had been trapped on Earth for centuries.
Meanwhile, Optimus Prime and the Autobots came to Earth looking for the Allspark, but they were too late. The First Decepticon Incursion began when Megatron launched an attack on the Human City of Los Angeles after the Human Military, after allying with Prime, moved the Allspark there. Optimus and his Human buddies fought off Megatron, and the Allspark was destroyed in their efforts to stop him.
Megatron was annihilated by the Allspark but even this did not stop him. Using ancient Transformer technology obtained from the Fallen, Starscream resurrected Megatron and the three Decepticon leaders brought out their backup plan: with the Allspark gone, they would make a new one. Fortunatly, Fallen happened to have a device specifically designed to do just that hidden away on Earth.
Meanwhile, Optimus Prime and the remaining Autobots call in reinforcements but they begin to worry as their supply of Energon is running low. They get word of Megatron's plan to find and aqquire a Solar Harvester, which would decompose Sol into pure Energon which the Decepticons could then collect. This became known as the second Decepticon incursion. Determined to stop them, Optimus and the Autobots intercept Megatron in an old warehouse where he is hiding, but Megatron calls in reinforcements and Optimus Prime is killed in the resulting battle.
Optimus's human buddies use a fragment of the Allspark to revive an ancient, deactivated Decepticon, Jetfire, who immidietly defects to the Autobots and tells them where they can find the Tomb of the Primes, which contains the Autobot Matrix of Leadership. Using Jetfire's advanced teleportation, the Humans recover te Matrix and use it to revive Optimus.
Fallen realises that he cannot activate the Harvester without the Matrix so he swoops in and steals it. Deprived of power, Optimus is on the verge of re-death. However, Jetfire sacrifices his parts and Energon to resurrect Optimus, gifting him with amazing 'flying' capabilities. Optimus swoops in, destroyes the Harvester rather half-heartedly and then beats the Energon out of the Fallen and Megatron, sucking the Energon out of the Harvester and into the Matrix. After killing Fallen and crippling Megatron, Optimus returns triumphantly to the Autobots, the source of unlimited power stored safely in his spark...
Megatron flees to Africa where he makes contact with Sentinel Prime, who had crashed on Luna all those years ago. Megatron tells him about the Matrix, which Sentinel wants for himself. Sentinel made plants for a Third Decepticon Incursion, pretending to be good and returning triumphantly to the Autobots. Sentinel asks Optimus for the Matrix but comes under attack from the Autobots themselves, who see through his deception. Enraged, Sentinel orders the Decepticons to attack the city of Chicago.
Optimus and the Autobots head there to destroy him, and Optimus engages him in battle. Sentinel beats him, however, and is about to kill him when Megatron attacks him from behind, reckoning that he should have the Matrix instead. Megatron asks for a truce from the weakened Primes, as long as he can be in charge. Optimus responds by ripping his spine out, and then shoots Sentinel in the face a few times for good measure. Now victorious, the Autobots settle on Earth, finally deciding that it is their new home.
Optimus uses the Matrix to quietly rebuild his race, hoping that one day they will be able to defend Earth from other alien terrors...
- Optimus Prime
- Jetfire (defected from Decepticons)
- a few other brave warriors