Settled by Polynesians some time between 124 and 1120, Hawaii was home to numerous independent chiefdoms. In 1778, British explorer James Cook was the first known non-Polynesian to arrive at the archipelago; early British influence is reflected in the state flag, which bears a Union Jack. An influx of European and American explorers, traders, and whalers arrived shortly thereafter, introducing diseases that decimated the once isolated indigenous community. Hawaii became a unified, internationally recognized kingdom in 1810, remaining independent until Western businessmen overthrew the monarchy in 1893; this led to annexation by the U.S. in 1898. As a strategically valuable U.S. territory, Hawaii was attacked by Japan on December 7, 1941, which brought it global and historical significance, and contributed to America's decisive entry into World War II. Hawaii is the most recent state to join the union, on August 21, 1959. In 1993, the U.S. government formally apologized for its role in the overthrow of Hawaii's government, which spurred the Hawaiian sovereignty movement.