The Timestrikers are an alien Faction attempting to over take Earth. Using military technology and energy leaks, they can invade different time epochs.
The Military had already known about the existence it seems of the Timestrikers, and had been monitoring them. However, they then believed that it was the Timestrikers causing massive energy leaks throughout the military bases causing rifts, allowing the Timestrikers to flood into our dimension. First attempting to take out a military installation, they mutated guards and soldiers, and added in their own forces as well. However they were pushed back by a Marine, who then followed them back to Ancient Egypt, where it seemed that they would take over the world from the past. Failing again, they escaped to Medieval times, and after that, left again to come back to the present. There, the last of the Timestrikers were defeated, and the world saved.