What is the purpose of these hostilities, and is the fate of humanity tied to the ultimate victor of these hostilities in some capacity?

The ultimate fate cannot be predicted with any certainty. What is desired is a displacement of the current rulers so the interlopers can step in and assume power of their empire. That is not an impossibility because it has happened numerous times in their history—the same as you have seen reflected in human history with the coming and going of dynasties and tyrants handing down power to their offspring and ruling as a true dynasty for centuries. So there is ample precedent for these kinds of incursions and it makes it tactically advantageous to engage in the location of a key outpost with the intention of gaining some leverage.