Although the military history of Oceania probably goes back thousands of years to the first human settlement in the region, little is known about war in Oceania until the arrival of Europeans. The introduction of firearms transformed conflict in the region; in some cases helping to unify regions and in others sparking large-scale tribal and civil wars. Force and the threat of force played a role in the annexation of most of Oceania to various European and American powers, but only in Australia and New Zealand did wars of conquest occur. Western Oceania was a major site of conflict in World War II as the Japanese Empire sought to expand southwards. Since 1945 the region has been mostly at peace, although Melanesia has suffered from Indonesian expansionism in some areas and civil wars and co