Earth

Earth is one of the terrestrial planets, third from the sun, and is the only planet with a naturally-occurring biosphere in the known universe, from which all life originated. It is the most dense planet in the solar system after Mercury was destroyed, with an atmosphere rich in oxygen, nitrogen, and carbon.

Military
Before the war, the only military force on Earth or anywhere were the combined forces of its component nation's armies, but when life began colonizing the solar system, the Expeditionary Defense Corps was originally founded to extradite criminals to the terrestrial authorities. When tensions flared between Earth and Pluto, the Terrestrial Defense Force was put together to defend the terrestrial planets from Plutonian attacks. Although the Expeditionary Defense Corps served as the main branch of the military, two more specialized branches were formed: the Astronautical Strategic Warfare Services and Astral Marine Corps. The ASWS was formed to handle both ship-to-ship as well as vessel boarding operations. The AMC was formed to specialize in forced entry on highly defended positions, such as colonial and station boarding offensives and planetfall operations.