The United Nations Trusteeship Council, one of the principal organs of the United Nations, was established to help ensure that non-self-governing territories were administered in the best interests of the inhabitants and of international peace and security. The trust territories – most of them former mandates of the League of Nations or territories taken from nations defeated at the end of World War II – have all now attained self-government or independence, either as separate nations or by joining neighbouring independent countries. The last was Palau, which became a member state of the United Nations in December 1994.