The Japanese military history spans a long time period of more than three millennia, from the Jomon (c.1000 BC) to the present. Following a long period in clan warfare that ended in the 12th century, came feudal wars which culminated into the Shogunate military government. Japanese history records that Japan was ruled by a military class and the Shogun for 676 years, from 1192 to 1868. The Shogun and the Samurai warriors were close to the top of the Japanese social hierarchy - only the aristocratic noblests outrank them nominally. From 1641 to 1853, Japan was effectively isolated from foreign influences by the sakoku policy. After the 1853 arrival of Admiral Perry and the 1868 elevation of Emperor Meiji, feudal militarism became imperialism. Japan's outlook was impacted by the imperialist policies of the West colonial powers. Japan is prohibited from using offensive war against other countries by the 1947 Japanese Constitution. In 1954, the Japan Self-Defense Forces was established.