The mission of the RMR is to act as a general reserve to the Royal Marines command and to promote a nationwide link between the military and civilian community.

They were mainly, but not solely, Royal Marines who had gained experience in World War II and trained in order to support the Corps against the threat from the Soviet Bloc.

Each of the main units acts as Headquarters for a number of smaller satellite detachments that spread out into the surrounding area to recruit locally in nearby population centers.

Recruits wear the blue beret with red badge backing issued to RM personnel who have not passed the commando course.

The course also introduces the recruits to CTCRM and provides an insight into the conduct of the commando tests while assessing the skills learnt and practiced at their unit.

Throughout Phase 1 training, weight is gradually added to the recruit's PLCE until it weighs the 22 lb (10.0 kg) required during the Commando Course.

This reflects the progression from individual shooting on a simple range to a live firing troop attack involving 30 Marines.

Once passed, recruits are awarded the cap comforter and may continue onto the final element of the course, the commando tests.

On successful completion of the RFCC, at the end of the 30 Miler, the RMR recruits are awarded the coveted green beret.

On earning their green beret following the completion of Phase 2 training, Marines join a 'Commando Company' within their RMR units.

Marines must then undertake Phase 3 training, which consists of a course at CTCRM practising troop attack exercises and amphibious assaults.

Only after completing this are Marines considered fully trained general duties rifleman, capable of serving with the regular corps.

As reservists progress through the ranks in the RMR, they can attend further courses in their chosen specialisation that are of a more advanced nature (e.g.. LC3 - Marine; LC2 - Corporal; LC1 - Sergeant).

In 2008, Royal Marine Reservist Lance Corporal Matthew Croucher received the George Cross for his actions whilst deployed with 40 Commando in Afghanistan.

The incident occurred whilst on a reconnaissance patrol, when upon entering a compound he felt himself activate a grenade tripwire.

He managed to cushion the majority of the blast with his Bergen whilst his body armour stopped further shrapnel, this left him with only minor injuries and his fellow Marines unharmed.