In August 1775, he arrived at the Dutch factory of the V.O.C. at Dejima, a small artificial island (120 m by 75 m) in the Bay of Nagasaki connected to the city by a single small bridge. However, like the Dutch merchants, Thunberg was at first rarely allowed to leave the island. These restrictions had been imposed by the Japanese "shogun" Tokugawa Ieyasu in 1639 after the Portuguese, who had been the first Europeans to arrive in Japan in 1543, persisted in missionary activity. The only locals who were allowed regular contact with the Dutch were the interpreters of Nagasaki and the relevant authorities of the city.