Following the disastrous landings at Gallipoli the British Government was not keen to consider amphibious landings within any future battle plans.
The Royal Marines however, were keen to learn from the lessons of the Great War.
Following the amalgamation of the RMLI and the RMA the Admiralty had consolidated the identity and role of the Corps to include the role of amphibious warfare.
This led to the Corps establishing a Mobile Naval Base Defence Organisation (MNBDO) and participating in the new Inter-Services Training and Development Centre (ISTDC).
The Royal Marines had already been involved with landing trials with the Royal Navy, but with this impetus, the Corps established a scheme for a Mobile Naval Base Defence Organisation (MNBDO).
An MNBDO would be able to set up an advanced base for the fleet in a time of war. Admiralty’s staff had worked up the experiments in 1920, but extra Government money was not forthcoming.
Therefore, much of what occurred during the early years of the MNBDO was funded on a shoestring budget. During the period of 1924 - 1930 only £10 000 was spent and the Corps utilised cast-offs from the Army’s Royal Engineers, including tractors and scaffolding.
In 1925 X Unit, the experimental branch of the MNBDO developed of techniques for landing artillery for advanced bases in Langstone Harbour, near Portsmouth.
During these experiments the Royal Marines developed their knowledge into beach inclines, the effect of the tide and the structure of the landing craft to ensure maximum effectiveness.
Later, they also developed techniques for landing tanks, provisions for mining equipment and the installation of searchlight and communications.
The MNBDO proved its worth in Alexandria, Egypt, following the Italian invasion of Abyssinia in 1935.
On their return, the Government allocated them more funding and a greater emphasis was put on the unit’s anti-aircraft capabilities.
During World War Two, the MNBDO and its sub-units were vital for the defence of the British Empire when they established advanced bases around the British Isles and in places such as Crete and the Indian Ocean.
The Royal Marines also participated in setting up the Inter-Services Training Development Centre (ISTDC) in Portsmouth. The ISTDC opened in 1938 and was the UK's first military agency specifically dedicated to combined operations.
The Government decided to locate the ISTDC within the Royal Marines Establishment in Eastney and it also had a Royal Marine representative, Captain Picton-Phillips, amongst the staff.
Staff at the ISTDC developed techniques for landing troops, equipment and supplies ashore including landing tanks, amphibious vehicles, troop landings by air and air supply of stores and equipment. The centre also produced a floating pier for landings.
The Government, however, turned down the ISTDC’s initial bid for funds for the creation of a Landing Craft Carrier.
In 1939 the ISTDC produced a report underlining the poor state of the country’s amphibious capabilities stating that no major landing attack could take place within six months of an order being given.
The Government granted the ISTDC funds for the construction of 18 small landing craft, 12 large landing craft and two support craft with armament and equipment.
By the outbreak of World War Two in September 1939 two prototype LCAs, the large landing craft carriers, were ready for trials and designs for LCM (1)s (Landing Craft Mechanised) and Landing Craft Support (Medium), or LCS (M), were also put into production.