Hell Day

We hope John Connor doesn't mistake this as Skynet's doing.

August 17, 2014, a date that became infamously known as Hell Day when the Decepticons, led by Shockwave, invaded and conquered Earth. As you might imagine, things did not go swimmingly for humanity after that.

Fiction

G.I. Joe vs. the Transformers

Following an attempt by Cobra to seize the Teletran 3 computer on Cybertron, Shockwave took control of it himself. Mastering its teleportation abilities, Shockwave was able to transport Decepticon forces to Earth. The planet was quickly ravaged by the Decepticons' superior technology and the surviving members of humankind were enslaved and put to work stripping the planet of its natural resources.

Only a small pocket of survivors led by Duke were able to hold out. It was into this world that Ratchet, a victim of a temporal displacement accident that had occurred during Cobra's original attack, turned up. When a group of Joes and Cobras arrived later in search of Ratchet, they found a desolate world plagued with Sweeps, Insecticons, and Ravages. Luckily, they also found Ratchet and returned him to the right time and place. G.I. Joe vs. the Transformers II #3 Events eventually played out in a way that prevented Shockwave from invading Earth, and thus the entire timeline unhappened. G.I. Joe vs. the Transformers II #4