The Solomon Islands are believed to have been inhabited by Melanesian people for thousands of years. The United Kingdom established a protectorate over the Solomon Islands in 1893. In the Second World War, there was fierce fighting between the Americans and the Japanese in the Solomon Islands campaign of 1942–45, including the Battle of Guadalcanal. Self-government was achieved in 1976 and independence two years later. The Solomon Islands is a constitutional monarchy with the Queen of the Solomon Islands, at present Elizabeth II, as the head of state.Since 1998, ethnic violence, government misconduct, and crime have undermined stability and society. In June 2003, an Australian -led multinational force, the Regional Assistance Mission to Solomon Islands (RAMSI), arrived to restore peace, disarm ethnic militias and improve civil governance.