The Japanese enlarged administration and appointed local leaders, which weakened the authority of local traditional leaders. Japan also tried to change the social organization in the islands from Matrilineality to the Japanese Patriarchal system, but with no success. Moreover, during the 1930s, one third of all land up to the high water level was declared the property of the Japanese government. On the archipelago, before it banned foreign traders, the activities of Catholic and Protestant missionaries were allowed. Indigenous people were educated in Japanese schools, and studied Japanese language and Japanese culture. This policy was the government strategy not only in the Marshall Islands, but on all the other mandated territories in Micronesia. On March 27, 1933, Japan handed in its notice at the League of Nations, but continued to manage the islands, and in the late 1930s began building air bases on several atolls. The Marshall Islands were in an important geographical position, being the easternmost point in Japan's defensive ring at the beginning of World War II.