The answer almost certainly lies in the deeply militaristic and authoritarian character of japanese society prior to 1945, and the culture of extreme brutality, fanaticism and racism that was deliberately encouraged in the japanese military during the 1930s. According to rummel, in china alone, during 1937–45, approximately 39 million chinese were killed, mostly civilians, as a direct result of the japanese operations and 102 million in the course of the war. The imperial japanese army air service took part in conducting chemical and biological attacks on enemy nationals during the second sino-japanese war and world war ii and the use of such weapons in warfare were generally prohibited by international agreements signed by japan, including the hague conventions (1899 and 1907), which banned the use of poison or poisoned weapons in warfare.
Interestingly, in the japan-china war in the 19th century, the japanese didn't treat the chinese as subhumans - the war was generally conducted in a civilised way, prisoners of war weren't mistreated, etc etc so obviously something changed in pretty short order. So we are left with question of what changed between world war i and the japanese invasion of china/pacific war the japanese during the russo-japanese war and world war i were trying to gain acceptance in the western dominated international community and this meant a degree of acceptance of western values.
Becoming syonan-to: the brutality of the japanese occupation from 1942 to 1945 more than 3 years of darkness in the light of the south. Not to mention germany, a western nation that didn't exactly set the high mark for morality during wwii i've lived in china, and read several historical military texts from both china and japan (eg, romance of the three kingdoms, tale of the heike, taiko, etc. For all beijing’s new-found interest in the story of “china’s auschwitz”, its retelling is unlikely to extend beyond 1945 for during the cultural revolution, the communist party accused many surviving prisoners of collaborating with the japanese and branded them traitors.
The japanese military during the 1930s and 1940s is often compared to the military of nazi germany during 1933–45 because of the sheer scale of suffering that both of them caused much of the controversy regarding japan's role in world war ii revolves around the death rates of prisoners of war and civilians under japanese occupation.
The japanese prime minister has china and south korea as an audience – but also his conservative base thomas peter/reuters people watch japan's prime minister shinzo abe on a screen as he gives a statement in tokyo aug 14, 2015.
By the autumn of 1932, all of manchuria was under japanese control in 1933, japan became the first country to withdraw from the league of nations after china requested an investigation into the japanese occupation revitalised by their coup, japan embarked on a military campaign aimed at destabilising north china. The site remembers hundreds of victims of a reported mass bayonetting by japanese troops during the second world war photograph: james wasserman/demotix for the guardian the taiyuan camp opened its gates in 1938 – one year after fighting between china and japan officially broke out – and closed in 1945 when the war ended.