In 1931, Lei returned to China and became a lecturer at the Sociology Department of Yenching University (later merged with Peking University). As
Japan invaded Manchuria and
encroached upon North China, Lei and her students joined the
December 9th Movement to demand that the
Nationalist Government resist Japanese aggression. After the
Marco Polo Bridge incident in 1937, the Japanese occupied Beijing and launched a full-scale war to invade China. Lei went to
Nanchang, Jiangxi Province to join the National Salvation Movement. She served in a women's advancement group which cared for wounded soldiers and was awarded the rank of
colonel. She also taught at a women's training class at the
Jiangxi Political Movement Institute, one of whose two deans was
Chiang Ching-kuo, the future President of the
Republic of China. When Nanchang fell to the Japanese in 1939, she moved to
Ji'an in southern Jiangxi, where she became a friend of the Communist leader
Zhou Enlai. In 1933, Lei published an article advocating
family planning. During the Sino-Japanese War, she wrote many essays based on her studies of women's lives, careers, and struggles in wartime. They were later published in the two-volume
Selected Works of Lei Jieqiong. In 1940, Lei helped to found Zhongzheng University (now
Nanchang University). A year later, she went to Shanghai where she became a professor at Soochow University and also taught at St. John's University, University of Shanghai, and Aurora University. In 1945, she cofounded the political party China Association for Promoting Democracy (CAPD) and would serve as its chairwoman decades later. After the end of
World War II in June 1946, the Shanghai Union of People's Associations sent 11 representatives, including Lei, to capital
Nanjing to petition the
Kuomintang government not to resume the
civil war against the Communists. When they arrived at
Xiaguan train station in Nanjing, they were assaulted by thugs and injured. The
Xiaguan incident raised an outcry in Chinese media, which blamed the KMT government for the attack. Zhou Enlai visited them in the hospital. At the end of the year, Lei returned to Yenching University and became a professor of sociology. ==People's Republic of China==