The New Republic Military Explained
After the defeat of the First Order, the New Republic senate realized that a central military was needed. A ratification of the Galactic Concordance stated that planets will still retain their respective militias, but the New Republic Military will act as both the primary military body and as a reserve force to be used in the event of war. Essentially the planetary militias were the National Guard from 21st Century America. The military is divided into three branches: Army, Navy, and Starfighter Corps. Various special forces exist within the branches, including the Army's Commandos and the Starfighter Corps' Rogue Squadron.