It is abnormal for a country to host foreign troops in peacetime.

For such a situation to remain in place, there must be an international agreement between the sender and receiver of the troops. In the case of U.S. armed forces stationed in Japan, the two countries have an agreement in the form of international law – in this case, the Japan-U.S. Security Treaty. In other words, U.S. forces are allowed to stay in Japan only under “the rule of law’ as stipulated by the treaty.