[3][4] The Admiralty appointed Madden Committee of 1924 proposed that a brigade of 3,000 Marines should be based ashore to "provide a striking force ... immediately available for use under the direction of the Naval Commander-in-Chief for amphibious operations, such as raids on the enemy coastline and bases ..." Peace-time finances had prevented the formation of such a force, but in September 1939 it was decided to raise a brigade of three light infantry battalions with around 2,000 men to fulfill this role.

By January it had been decided to expand the brigade to four battalions, but the first recruits did not reach them from the Royal Marine Special Reserve Depot until April 1940.

By June that force had been relieved and in the wake of the Dunkirk evacuation, and the RM Brigade was placed on standby in Pembrokeshire to counter any threat of German occupation of neutral Ireland.

By July the concern shifted to a potential German occupation of the neutral Portuguese islands of the Azores and Cape Verdes, with the RM Brigade relocating around Plymouth as a departure port, and undertaking coastal defence duties while they waited.

Despite extensive training in beach assault landings, proposals for use of the RM Division in the Lofoten Islands Raid in December 1941 were rebuffed in favour of the Commandos.

This expanded Division was originally assembled to provide a force to invade the Canary Isles, should Spain enter the war on the side of the Axis powers, and was then held on standby by General Harold Alexander for a range of potential amphibious operations.

The last of these was Operation Ironclad, with Major-General Sturges taking part of the RM Division HQ to head up Force 121 for the amphibious assault on Diego-Suarez in may 1942.

However, despite supporting representations from Admiral Mountbatten who was then Chief of Combined Operations, the War Office considered the light infantry units of the Royal Marine Division to be unsuitable for the task.

[5] Vice-Admiral Louis Mountbatten, Chief of Combined Operations, having "made friends with the division in Wales" lobbied hard for its deployment in its intended role, as an amphibious assault force.

However, this had been repeatedly blocked by the Army on the basis that it lacked the heavy weapons and logistical support needed to maintain itself in the field after an initial assault.