In the summer of 1937, shortly after the Marco Polo Bridge incident, Guo returned to China to join the anti-Japanese resistance. His attempt to arrange for Sato Tomiko and their children to join him in China were frustrated by the Japanese authorities, and in 1939 he remarried to Yu Liqun [zh], a Shanghai actress. After the war, Sato went to reunite with him but was disappointed to know that he had already formed a new family and returned to Japan. (According to some Chinese text articles, his behavior towards her was "shameless" 无耻. For example, he refused to meet her when she went to see him in Hong Kong, 1948.)
1939 "Shi Gu Text Research"《石鼓文研究》published. April 1940 archeology dig of Han tomb in Chungking which resulted in this study of the first known stone carved calligraphy. This dig was controversial since some archeologists were concerned about preservation. But Guo did his research and wrote his paper anyway.