Pearl Harbor was once an extensive, shallow embayment called Wai Momi (water of pearl) in the region of Pu'uloa (long hill) by the Hawaiians. The first people to arrive on the island of O'ahu (around 100 to 300 BCE) would have seen verdant lands around the bay watered by streams running down from the Ko'olau Mountains, bordered by the arid 'Ewa Plain with its abundance of flightless land birds. Polynesian settlement, British arrival, sugarcane plantations, and U.S. military development have drastically changed the landscape and decimated the native bird population. Currently an active military base and the home of America's Pacific Fleet, Pearl Harbor was also the site of the infamous Imperial Japanese Navy attack of December 7, 1941, which launched the United States into World War II.