what's the difference between the army and the royal marines
Royal Marines The Corps of Royal Marines (RM) is the amphibious light infantry and one of the five fighting arms or branches of the Royal Navy.[2][3] The Royal Marines were formed in 1755 as the Royal Navy's infantry troops. However, the marines can trace their origins back to the formation of the English Army's "Duke of York and Albany's maritime regiment of Foot" at the grounds of the Honourable Artillery Company on 28 October 1664.[4]
First sergeant In the United States Marine Corps, first sergeant (abbreviated 1stSgt) is one rank above gunnery sergeant and one pay grade below sergeant major and master gunnery sergeant. It is equal in grade to master sergeant (E8), although the two ranks have different responsibilities. A first sergeant has command leadership responsibilities and serves as the senior enlisted adviser to the commander at the company, battery or detachment level, while master sergeants have technical responsibilities within their respective occupational fields, and serve important leadership roles within various company or battery sections. Master sergeants may also perform staff functions at the battalion/squadron level or above. Unlike first sergeants and master sergeants in the U.S. Army, no lateral movement is possible between the two ranks in the Marine Corps; they're permanent appointments and require a change in occupational specialty. Rather, gunnery sergeants elect a preference on their fitness reports, which are considered before promotion. Ultimately, those selected for either rank are appointed based on suitability, previous duty assignments, and the needs of the Marine Corps. Later in their careers, first sergeants are eligible to be considered for promotion to sergeant major, while master sergeants would be on the career track for master gunnery sergeant.