A navy is the branch of a country's military forces principally esignated for naval warfare and amphibious warfare namely lake- or ocean-borne combat operations and related functions. It includes operations conducted by surface ships, amphibious ships, submarines, and seaborne aviation, as well as ancillary support, communications, training, and other fields; recent developments have included space related operations. The strategic offensive role of a Navy is projection of force into areas beyond a country's shores (for example, to protect sea-lanes, ferry troops, or attack other navies, ports, or shore installations). The strategic defensive purpose of a Navy is to frustrate sea-borne projection-of-force by enemies. The strategic task of the navy also may incorporate nuclear deterrence by use of nuclear missiles.