Prior to World War 2, Koreans sought asylum and educational opportunities that were available in Japan.In 1910, the Japan-Korean Annexation Treaty was established and stated that Koreans were to be considered Japanese as citizenship by law as Korea was annexed by Japan. During World War 2, Japanese government established the National Mobilization Law, which constrained Koreans from getting jobs, which were very limited for Koreans even prior to World War 2. Koreans that were not constricted were forced to work in factories and mines in inhumane conditions;[9 an estimated 60,000 Koreans died because of work conditions. Following World War 2, Koreans decided to participate in the Post-world war 2 illegally because of the unfair treatment and wages in Japan both politically and economically. "Zainichi" (resident in Japan) Koreans are permanent residents of Japan registered as Joseon (Korean: 조선, Japanese: Chōsen, 朝鮮) or South Korean nationality. Joseon was annexed by Japan in 1910, therefore Zainichi Koreans with Joseon citizenship are de facto stateless. After World War II, 2 million Koreans living in Japan were granted a temporary Joseon nationality under the US military government (because there was no government in Korea then). However, the meaning of Joseon nationality became vague as Korea was divided by the United States and the Soviet Union, and in 1948 North and South Korea each established their own government. Some obtained South Korean citizenship later, but others who opposed the division of Korea or sympathized with North Korea maintained their Joseon nationality because people are not allowed to register North Korean nationality.