Marines (from the English adjective marine, meaning of the sea, from Latin marinus ("maritime"), via French marin(e), of the sea) are military forces optimised for operations at sea. Historically marine forces are part of a navy. However, in some countries the marine force is under independent command.
Tasks undertaken by marines have included providing security in a warship whilst at sea, reflecting the pressed nature of the ships' company and the risk of mutiny. Other tasks would include boarding of vessels during combat or capture of prize ships and providing manpower for raiding ashore in support of the naval objectives. Marine elements would also contribute to the campaign ashore, in support of the military objective.
With the industrialization of warfare in the 20th Century the scale of landing operations increased, and 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.