Royal Marines

The Corps of Her Majesty's Royal Marines, commonly just referred to as the Royal Marines (RM), are the marine corps and amphibious infantry of the United Kingdom and, along with the Royal Navy and Royal Fleet Auxiliary, form the Naval Service.[3] They are also the United Kingdom's specialists in amphibious warfare, including the operation of landing craft; mountain warfare; and Arctic warfare. A core component of the country's Rapid Deployment Force, the Corps's 3 Commando Brigade is capable of operating independently and is highly trained as a commando force. It is trained to deploy quickly and fight in any terrain. The Royal Marines have the longest basic infantry training course of any NATO combat troops.

(From wikipedia)