was known as (Dutch studies). It became obsolete after the country was opened and the policy collapsed. Thereafter, many Japanese students (e.g., Kikuchi Dairoku) were sent to study in foreign countries, and many foreign employees were employed in Japan (see ). The policies associated with ended with the Convention of Kanagawa in response to demands made by Commodore Perry. Challenges to seclusion Many isolated attempts to end Japan's seclusion were made by expanding Western powers during the 17th, 18th and 19th centuries. American, Russian and French ships all attempted to engage in a relationship with Japan but were rejected. In 1640, the Portuguese out of Macau sent envoys to convince the shogunate to reverse their recent expulsion and cessation of trade. They were captured, their ship burnt, and 61 members of the mission were executed by order of the bakufu, on August 4. In 1647 Portuguese warships attempted to enter Nagasaki. The Japanese formed a blockade of almost 900 boats to stop the ships. After the event, the Japanese added more security to Nagasaki as fears rose that other countries would challenge the new seclusion policy and attempt to enter through Nagasaki. In 1738, a three-ship Russian naval squadron led by Martin Spanberg visited the island of Honshu. The Russians landed in a scenic area which is now part of the Rikuchu Kaigan National Park and reported civil treatment. Spanberg led two further voyages in Japanese waters in 1739 and 1742, helping advance Russian interests in the Kurils. In 1778, a Russian merchant from Yakutsk by the name of Pavel Lebedev-Lastochkin arrived in Hokkaidō as part of a small expedition. He offered gifts, and politely asked to trade, but in vain. In 1787, Jean-François de Galaup, comte de Lapérouse navigated in Japanese waters. He visited the Ryūkyū islands and the strait between Hokkaidō and Sakhalin, naming it after himself. In 1791, two American ships commanded by the American explorer John Kendrick—the Lady Washington, under Captain Kendrick, and the Grace, under Captain William Douglas—stopped for 11 days on Kii Ōshima island, south of the Kii Peninsula. Kendrick was the first known American to have visited Japan. He apparently planted an American flag and claimed the islands, although only one English-language account of the voyage exists. In 1792 the Russian subject Adam Laxman visited the island of Hokkaido. From 1797 to 1809, several American ships traded in Nagasaki under the Dutch flag,