The Royal Marines (RM) are the marines and amphibious infantry of the United Kingdom and, along with the Royal Navy and Royal Fleet Auxiliary, form the Naval Service . They are also the United Kingdom's amphibious force and specialists in mountain and Arctic warfare. A core component of the country's Rapid Deployment Force, the Corps is able to operate independently in all types of terrain and is highly-trained as a commando force. It is a force designed to be able to quickly deploy and fight in any terrain in the world.