U.S. amphibious warfare began its development in the early 1900's, became a real capability in World War II, and today provides the nation with a means to achieve its policy objectives with an ability to project military power from the sea. During World War II, the first real test of this amphibious assault capability came at the beginning of the Central Pacific drive on Tarawa in 1943 and culminated with the final amphibious operation in the Pacific at Okinawa, some 350 miles south of mainland Japan. Ultimately, the U.S. military's tactics, techniques, and procedures for conducting amphibious operations in the Pacific theater during World War II became more efficient as the war progressed, largely due to an increased understanding of the requirements for success in the combat environment, and an emphasis on meeting and exceeding those needs.