Prairie of Darkness

It is 1800's USA. The country is divided, and as a member of the US Army, you get posted to a fortress on the edge between endless grassland and civilization. During  a sneak CSA attack on the fortress, you and your squad are forced to retreat west into wild untamed country. However it seems something else is lurking in the tall grass, and it is certainly not human. In fact, it may not even be living.... Can you survive? Can you find your way back? With no readily available ammunition, food or water, hope dwindles as your squad gets picked off one by one until you are the only one left.  Wait... what is that in the grass?!