‘Lord Spencer's augmentation of that most useful body of men [my emphasis], the Corps of Marines, is, like every measure of his administration, dictated by the most earnest desire to promote the good of the Service, and the consequent welfare of his Country.’ The description of the Marines being ‘that most useful body of men’ was common in the press and literature in the second half of eighteenth-century Britain. The British Marine Corps, while a branch of the Royal Navy and subject to its control and pay, also had many independent elements. While the Army and Navy were always much larger, the size of this junior service in voted strength hovered between 3,600 to nearly 30,000 men in the 47-year period from its reformation in 1755 as the Corps of Marines until 1802 when it was formally accepted by the King as Royal Marines. Marines comprised between 11 and 30 per cent of the overall voted strength for the Navy in this period.

Marine forces are not unique to Britain, and in many ways are as old as warfare at sea. For example, in 256 B.C. the Roman Republic was able to station between 120 to 200 Marines – a larger complement than a first-rate ship-of-the-line in the eighteenth century – on the upper-decks of their largest ships. These marines were little more than regular legionaries who would fight their battles at sea similar to those on land, hence the development of the corvus in the First Punic War.