Complex sentence: The Terran Federation's military appears to be divided into either Army or Navy (that use spacecraft instead of ships and double as an air force), with dozens of non-combat and support branches e.g logistics, biological/chemical weapons development, and terraforming.
Split into simpler sentences: The Terran Federation's military appears to be divided into an Army and a Navy (that use spacecraft instead of ships and doubles as an air force). The dozens of non-combat and support branches include units for logistics, biological/chemical weapons development, and terraforming.