Nagasaki is the capital and the largest city of Nagasaki Prefecture in Japan. It was known for being a major trading center between Japan and the outside world after Portugal established trading relationships with Japan in the 16th century. By the time Japan went into a state of seclusion during the Tokugawa era, foreign and outside commerce continued unabated and exclusively in Nagasaki through the Dutch. During World War II, Nagasaki was the second city after Hiroshima in Japan that experienced a nuclear attack.