After the North China Incident, tensions were running high in Tianjin. In July 1937, the Japanese Army attacked Tianjin and occupied the university on the 30th. Nankai University was the first victim of the Anti-Japanese War among Chinese higher education institutions. It was estimated that the loss of property amounted to about three million francs, making up one tenth of all the war damage to Chinese higher education institutions.
On the afternoon of the 30th, Zhang Boling gave a speech to a journalist of Central Daily News. He said, “The enemy bombarded Nankai University. What was ruined was the material of Nankai; the spirit of Nankai will strive to be stronger in spite of the disaster. ”
In August 1937, Nankai, together with Peking and Tsinghua universities, united in Changsha to form Changsha Temporary University. Zhang Boling, Jiang Menglin and Mei Yiqi, presidents of the three universities, worked together as members of the Standing Committee to chair the School. The temporary university was located in Jiucaiyuan in the east of Changsha city. On the 1st November, 1937, Changsha Temporary University officially began the semester. This date has become the anniversary of the National Southwest Associated University.
On the 2nd April, 1938, Changsha Temporary University was moved to Kunming and changed its name to Southwest Associated University. On the 30th November, the motto of the university was established as Perseverance and Persistence. In 1939, the Economic Institute of Nankai was transferred to Nankai Middle School, located in Shapingba, Chongqing, where it continued to recruit graduates. In July 1942, the Research Center of Frontier Humanities was set up in Kunming and Frontier Humanities was published. During the Southwest Associated University period, the three schools, standing through thick and thin, produced a great number of noted scientists and patriotic revolutionaries.
The concentration of luminaries among the teaching staff of Southwest Associated University was unique in the modern history of Chinese education. During these eight years, there were 290 professors and forty-eight vice professors, with more than 8,000 students and 2,500 graduates, of whom seventy-eight later became academicians of the Chinese Academy of Sciences; twelve became members of the Chinese Academy of Engineering; two won the Nobel Prize in Physics; three won the State Preeminent Science and Technology Award; and eight won the medal for meritorious service in bomb and satellite research. A large group of social scientists, litterateurs, politicians, revolutionaries, and even government leaders were tightly connected with the university, including Li Guangtian in the Department of Literature, Bian Zhilin and Liu Wuji in the Department of Foreign Languages, Lei Haizong and Zheng Tianting in the Department of History, Feng Wenqian in the Department of Philosophy and Psychology, Huang Yusheng and Zha Liangzhao in the Normal College, Chen Xujing in the Department of Law and Business, Jiang Lifu and Chen Xingshen in the Department of Mathematics, Rao Yutai and Wu Dayou in the Department of Physics, Yang Shixian and Qiu Zongyue in the Department of Chemistry, and Meng Guangzhe in the Department of Engineering.