Amphibious am FIHB ee uhs, warfare, is the conduct of military operations by naval, air, and land forces for the purpose of seizing a beach or coastal area. Amphibious operations are generally considered the most complex form of warfare. In the Pacific Ocean region during World War II (1939-1945), a common objective of United States amphibious operations was to seize islands on which to build advance air and naval bases for operations against Japan.