Most reasons for anti-Japanese sentiment in China can be directly traced to the Second Sino-Japanese War , which was one theatre of World War II . As a consequence of the war , China suffered 7 million to 16 million civilian deaths and 3 million military casualties . In addition , the war caused an estimated $ 383.3 billion USD in damage and created 95 million refugees . Manchuria came under Japanese control in 1931 as a state named Manchukuo . Many major cities thereafter , including Nanjing , Shanghai , and Beijing were occupied in 1937 by the Japanese . Notable incidents included the Nanking Massacre . In Manchuria , Unit 731 , a medical unit of the Japanese army , researched biological warfare using Chinese civilians as test subjects , who were referred to as human ' logs ' in the medical journals . Women from many Asian countries , including China , were made to serve as prostitutes in military brothels ( and were often referred to as " comfort women " ) under Japanese occupation
Unit 731
Unit 731
Anti-Japanese sentiment in China