 ESGs allow the U.S. to provide highly movable and self-sustaining naval forces for missions in various parts of the world.The ESG concept combines the capabilities of surface action groups, submarines, and maritime patrol aircraft with those of amphibious ready groups and Marine expeditionary units (special operations capable) to provide greater combat capabilities to theater combatant commanders.An expeditionary strike force (ESF) integrates the CSG and ESG with the sea-basing functions provided by the maritime prepositioning force (future) to provide an even more potent capability.