Early 20th Century

The Royal Marines also played a prominent role in the Boxer Rebellion in China (1900), where a Royal Marine earned a further Corps Victoria Cross. For the first part of the 20th century, the Royal Marines' role was the traditional one of providing shipboard infantry for security, boarding parties and small-scale landings. The Marines' other traditional position on a Royal Navy ship was manning 'X' and 'Y' (the aftermost) gun turrets on a battleship or cruiser. During both World War I and World War II Royal Marine detachments were limited to Cruisers and above and until the latter part of the 20th century Royal Marine Bands were also carried on those ships. In times of war the Bandsmen traditionally operated the ship's comprehensive fire-control system, situated for stability and safety at the lowest deck of the ship. Consequently, when ships were sunk, almost inevitably the entire ship's band was lost.

Pursuing a career in the Marines had been considered 'social suicide' through much of the 18th and 19th centuries since Royal Marine officers had a lower standing than their counterparts in the Royal Navy. An effort was made in 1907 through the common entry or "Selbourne Scheme" to reduce the professional differences between RN and RM officers. This provided for an initial period of service where both groups performed the same roles and underwent the same training. Upon promotion to Lieutenant officers could opt for permanent service with the Royal Marines. The scheme was abandoned after three years when only two of the new entrants chose this option over that of service as naval officers, for whom promotion prospects were much greater. At the outbreak of World War I, the Corps was 58 subalterns under establishment.