The URC is a direct result of the UGI training a colonies militia but doing so caused the URC to rise as they were angry at the UGI for uknown reasons but their leader wasn't making his reasons known. The URC continued to be a threat for over 17 years after Operation Sandoval. During the Operation the leader survived but 4400 of his fighters ended up dying int he process. Its unknown how many fighters there are in the URC but they wear the Militia uniform of combat armor and a beret.
The URC wasn't a major threat to the UGI as a whole but only to the planet Sandoval.