As for the second Sino-Japanese war, the imperial Japanese army consistently regarded the war not as a formal war but as a binational conflict which lacked any formal declaration of war. Hence, they professed that they neither needed nor would take captives according to the international laws.
In the consequence, a very strange situation had occurred; the then Japanese records about this war rarely mentioned Chinese captives, although the Chinese army mobilized about FOUR MILLION soldiers on this war!
This fact strongly implies that the Japanese army illegally executed several hundred thousand Chinese captives, and connotes that other reported Japanese cruelties were also the truth.