 Chang spent two years on research for the book . She found source materials in the US , including diaries , films , and photographs of missionaries , journalists , and military officers who were in Nanjing at the time of the massacre . Additionally , she traveled to Nanjing to interview survivors of the Nanking Massacre and to read Chinese accounts and confessions by Japanese army veterans . Chang did not , however , conduct research in Japan , and this left her vulnerable to criticisms on how she portrayed modern Japan in the context of how it deals with its World War II past . 
