The Horde, having been attacked by two fronts, and under their animalistic instincts, have decided to charge and attack the 3rd Empire and The Confederacy. Turn Order = The 3rd Empire ---> The Horde ---> CSA ---> 3rd Empire The Walkers are the only types of zombies that made it to the US, along with a few Runners, so naturally, they make it to the frontlines first and can take out some but not all soldiers; it's when the Walkers get to the frontline that things get bad. The numbers, the sheer number of the infected Portugalians and Americans will overwhelm the frontlines, amounting to a whopping 860K Walkers and 20 Runners.