Nature's Way

It was a simple, random mutation, but it spelled doom for mankind. The shattered remnants of the 45th Division are fighting a hopeless rearguard to hold the Red River, in Oklahoma. They are exhausted and demoralized by their losses, with worn out equipment and short on supplies, but they can't retreat. This is our last viable defense line guarding the Midwestern Grain Belt. Lose that, and it's all over. The fight is eating them up, they have no hope and nowhere to go, and the ants just keep coming.
This is the last day of mankinds' last stand against Nature out for revenge.