Status Updates From Transformers vs. The Termin...

As the Autobots, Sarah Conner and the T-800 set their marks on finding the Decepticons, the Decepticons make it to Cyberdyne Systems manufacturing plant to gain the most energon that they can as well as exterminate the human race. They make it and a war ensutes. The T-800 sets a bomb on a Decepticn that was also in the Ark, resulting in the rest of the Autobots on the ark to perish.

Sarah inadvertedly revived Optimus and Bumblebee, so now Optimus fights back against the Decepticons as they retreat. Then they find the t-800 as it tries to end Optimus before Sarah ends the confrontation to figure out what in the world is going on. Then the t-800 explains how in the future, the cybertronians wiped out all of mankind and how Skynet was their only means of protection.