Gaiaterra: Elysea's Conflict/The Matrix War

The Matrix War, was a major armed conflict that began in 2029 V.C., triggered when SKYNET managed to hack into the Elswords Empires nuclear armament, intending to launch their entire arsenal to wipe out Gaiaterra in nuclear fire, causing Optimus Prime, one of the few AIs who developed compassion to life, to rebel along with countless other AIs. Causing a war across the globe as SKYNET sends its army out among Gaiaterra, forcing the other nations to defend their homeland, allowing SKYNET to get the codes while they were distracted, with only Optimus, the island he allied with, and the Elsword Empire, being the only ones who know SKYNET's true goal and fight to stop him. Ending with the formation of the Guardians Of Gaiaterra.

In Gaiaterra: Elysea's Conflict, It is the DLC Tacitus, and origin, story for the Guardians of Gaiaterra.

Rise Of The Machines
"In time, we realized that SKYNET didn't intend to conquer us with it's hordes of machine, that it was just a distraction while it went for its true goal. But what that goal is we don't know. And the Empire aren't giving any hints..."

-Aquilan General John Connors, retelling the events of the Matrix War

Defying Judgement Day, The Final Battle Against SKYNET
"SKYNET must be stopped, no matter the cost."

-Optimus Prime, toward the now formed Guardians, before the final battle of the Matrix War

On the season of Aion 59, 2029 V.C. SKYNET had all of the Empires launch codes and began decrypting them, and within 24 hours he would have access to the Empire's nuclear stockpile and wipe out all of Gaiaterra. The Empire brutally decimated in their vain attempts to stop him, while the other nations were too busy defending themselves to know of SKYNET's true plan, SKYNET, at a glance, had won.

Yet there was still one nation that knew of his true goals and still fights. The nation of Atlatea and the defectors of SKYNET led by Optimus, now christened the Autobots, united as the Guardians of Gaiaterra and planned one of the greatest invasion on Matsushima Island in a last-ditch attempt to stop him. An untold battle that saved millions, yet only known by the Guardians, Empire, and SKYNET, known as Defying Judgement.

Trivia

 * The campaign, if you can't guess it, is based off Judgment day from the Terminator series, with SKYNET wiping out most of humanity with nukes, except in this world he was stopped by Optimus Prime.