A carrier strike group is a type of carrier battle group of the United States Navy. It is an operational formation composed of roughly 7,500 personnel, usually an aircraft carrier, at least one cruiser, a destroyer squadron of at least two destroyers or frigates, and a carrier air wing of 65 to 70 aircraft. The carrier strike group is a flexible naval force that can operate in confined waters or in the open ocean, during day and night, in all weather conditions. The principal role of the carrier and its air wing within the carrier strike group is to provide the primary offensive firepower, while the other ships provide defense and support. These roles are not exclusive, however. Carrier strike groups are tasked to accomplish a variety of wartime missions, as well as a wide variety of functions in situations short of war. The peacetime mission is to conduct forward presence operations, to help shape the strategic environment, deter conflict, build interoperability with allies, and respond to crises when necessary.