The Shimazu daimyo of Satsuma-han maintained indirect contact with the China mainland throughout most of the Tokugawa period. This contact was possible despite the seclusion policy of the Tokugawa government which prohibited Japanese from going abroad and the policy of the Ming dynasty which would not allow Chinese to trade with Japanese. The link between Satsuma and China was die Ryukyu kingdom. Through the Ryukyu Islanders, the Shimazu daimyo obtained valuable Chinese commodities which were then sold for a profit to other parts of Japan. This commercial activity was a breach in the shogun's monopoly of foreign trade, which was supposed to be confined to the single port of Nagasaki.