Marine infantry

Marines, also known as a marine corps or naval infantry, are an infantry force that specializes in the support of naval and army operations at sea and on land, as well as the execution of their own operations. In the majority of countries, the marine force is part of the navy, but it can also be under the army like the Troupes de marine (French Marines) and Givati Brigade (Israeli Marines), or form an independent service branch like the United States Marine Corps (although the United States Marine Corps is under the United States Department of the Navy).

Historically, tasks undertaken by marines have included: helping maintain discipline and order aboard the ship (reflecting the pressed nature of the ships' company and the risk of mutiny), the boarding of vessels during combat or capture of prize ships, and providing manpower for raiding ashore in support of the naval objectives.

With the industrialization of warfare in the 20th century the scale of landing operations increased; this brought with it an increased likelihood of opposition and a need for co-ordination of various military elements. Marine forces evolved to specialize in the skills and capabilities required for amphibious warfare.

In the earliest day of naval warfare, there was little distinction between sailors and soldiers on a warship. The oarsmen of Ancient Greek and Roman ships had to be capable of fighting the rowers of opposing ships hand-to-hand; though hoplites began appearing on Greek ships specifically for the boarding of enemy ships. The Romans were the first to understand the importance of professional soldiers on board of ships. Since during the first punic war Roman crews remained inferior in naval experience to the Carthaginians, and could not hope to match them in naval tactics, which required great maneuverability and experience. They therefore employed a novel weapon which transformed sea warfare to their advantage. They equipped their ships with the corvus, possibly developed earlier by the Syracusans against the Athenians. This was a long plank with a spike for hooking onto enemy ships. Using it as a boarding bridge, marines were able to board an enemy ship, transforming sea combat into a version of land combat, where the Roman legionaries had the upper hand. During the early Principate, a ship's crew, regardless of its size, was organized as a centuria. Crewmen could sign on as marines (Called Marinus), rowers/seamen, craftsmen and various other jobs, though all personnel serving in the imperial fleet were classed as milites ("soldiers"), regardless of their function; only when differentiation with the army was required, were the adjectives classiarius or classicus added. The Roman Navy's two fleet legions, I Adiutrix and II Adiutrix, were among the first distinct naval infantry units .

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