The Republic Defense Coalition, also referred to as the Republic Defense Corps, (RDC) functioned as a Galactic Republic entity designed for defense and management of crises. It operated through a collection of agreements that vested the central government with authority over local planetary defense forces during times of emergency, given the Republic's lack of a permanent military. These forces remained under the RDC's command until the crisis was resolved, at which point they were returned to their respective home planets and RDC operations would cease.
Individuals serving within the Republic Defense Coalition were designated as RDC crewmembers. These crewmembers held ranks such as corporal, who, according to the established hierarchy, reported to higher-ranking RDC officers. Despite his rank and role as a scientific officer, Elping Tsoo did not consider himself an officer. The RDC also included a formation of troopers. For the majority of these troops, the Republic enjoyed a period of peace, making the Nihil conflict their initial experience in actual combat.
Around the time of the Great Hyperspace Disaster in 232 BBY, the Republic did not feel the need to maintain a standing army, as the expanding Hutts remained peaceful and the Mandalorians had been inactive for a considerable period. The RDC instead relied on its Emissary-class cruisers, along with smaller vessels, for support. However, in the event of a significant threat, the RDC could activate treaties with Republic worlds such as Alderaan and Chandrila, requesting ships and personnel, which would be returned after the emergency subsided.
In 232 BBY, the Hetzal system faced a threat when a freighter named the Legacy Run was destroyed in hyperspace, resulting in anomalies being projected toward the system's three inhabited planets. RDC ships were present in the Outer Rim for a meeting between the Jedi Order and the Republic on the Starlight Beacon space station, and consequently, the Third Horizon was dispatched to protect the star system, under the command of Jedi Master Avar Kriss.
In 230 BBY, a group of RDC vessels sent to the Outer Rim following the destruction of Starlight Beacon were destroyed during hyperspace travel by stormseeds when they attempted to enter sectors controlled by the Nihil.