The temporary attachment of the 8th Argylls over the winter of 1940-1 enabled the RM Division to develop new techniques in landing heavy weapons and training regular army troops in amphibious operations, and this was extended under Major General Sturges by the attachment of the 29th Independent Infantry Brigade in May 1941. 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 to deny that harbour to the new Japanese threat. 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. The Admiralty refused to approve the RM Division being brought up to a standard establishment, and so their place was taken by two brigades of 5th Division.