The Royal Marines Reserve (RMR) is the volunteer reserve force used to augment the regular Royal Marines in times of war or national crisis. The RMR consists of some 750 trained ranks distributed among the four units within the UK. About 10 percent of the force are working with the Regular Corps on long-term attachments in all of the Royal Marines regular units. All the volunteers within the RMR must pass through the same rigorous commando course as the regulars. The former may be civilians with no previous military experience or may be former regular Royal Marines.