PACIFIC OCEAN (July 27, 2012) The aircraft carrier USS Nimitz (CVN 68) and the amphibious assault ship USS Essex (LHD 2) are underway in close formation during the Rim of the Pacific (RIMPAC) 2012 exercise. Twenty-two nations, more than 40 ships and submarines, more than 200 aircraft and 25,000 personnel are participating in the biennial RIMPAC exercise from June 29 to Aug. 3, in and around the Hawaiian Islands. The world's largest international maritime exercise, RIMPAC provides a unique training opportunity that helps participants foster and sustain the cooperative relationships that are critical to ensuring the safety of sea lanes and security on the world's oceans. RIMPAC 2012 is the 23rd exercise in the series that began in 1971. (U.S. Navy photo by Mass Communication Specialist 3rd Class Raul Moreno Jr./Released)