The second Sino-Japanese War is usually folded into World War II, but the conflict between Japan and China began prior to the attack on Pearl Harbor. Japan launched an invasion of Manchuria in 1931 and over the next several years expanded further into other areas. On December 13, 1937, the Chinese city Nanking. Once the army took the city, Japanese soliders rounded up Chinese men. They were taken to the outskirts of the city and shot, stabbed, or set on fire. Between 20,000-80,000 Chinese women were raped. Japanese soldiers engaged in numerous gruesome acts of cruelty: they disemboweled women, forced fathers to rape their daughters, and stabbed infants with bayonets. They buried people alive and set people on fire. The massacre began in December 1937 and continued until January 1938. Several Westerners were living in Nanking when it was sieged and fifteen of them established a Safety Zone to try and protect the Chinese refugees. Approximately 300,000 noncombatants were slaughtered.
These links can help you start (or continue) exploring this atrocity from a variety of perspectives. Library resources such as Tripod and Proquest often work better for academic research than just using Google, because you will be more likely to find academic sources (e.g. peer-reviewed journal articles).
There are strategies for searching databases (and Google) more effectively, and Swarthmore's librarians would be happy to share their knowledge with you. Contact Anne Garrison (Humanities Librarian - agarris1@swat) or Sarah Elichko (Social Sciences Librarian selichk1@swat) to get some tips for your research.