Marines with 2nd Battalion, 7th Marine Regiment make camp as the USS Button rests in the background during Pacific Horizon 2011 - a maritime prepositioning force exercise - aboard Camp Pendleton, Calif., March 2. Pacific Horizon is a combined exercise between the I Marine Expeditionary Brigade and the Navy’s Expeditionary Strike Group-3. The exercise is part of an annual training plan that prepares Navy and Marine Corps forces to conduct selective offload and at-sea transfer of personnel and equipment from sealift platforms to amphibious ships, or directly to air and surface craft capable of ship-to-shore delivery. The U.S. keeps maritime prepositioning squadrons forward-postured where they can quickly close on littoral areas of vital national interest in the event of crisis. Merging the weight and volume advantages of sealift with the speed of airlift, maritime prepositioning enables sailors and Marines to link up with assets at sea to respond with speed and effectiveness in support of our nation's strategic interests.