And not to dredge up the entire episode since we are all pretty familiar with the atrocity. Did you ever (personally) wonder where the photos of the Japanese soldiers committing those things came from? I know I did, and couldn't really figure it out until I read the book Stillwell by Tuchman. I had considered they had been taken by either missionaries, or John Rabe the German businessman in Nanking at the time, but that didn't explain how they ended up in American newspapers so soon after the event. Turns out they were taken by the Japanese themselves to document their "fun" for their family members, but since they didn't have photo-darkrooms in tow with them they took them to local photo shops for developing. The photo shop owners simply ran off extra copies, and shipped them out of China to the rest of the world.
That makes sense, negatives have been found as well , and not only about Nankin, but in every occupied country .
They thought they were going to win those days, so they didn't bother about hiding there crimes. In fact they quite often posed without thinking their pictures could later be used as evidence.
Their arrogance and pride came back to bite them. Humility and modesty is underrated. The photos may have gotten the commanders convicted after the war, but the rank and file of the Japanese 6th ID had justice administered to them by the US 37th ID on Bougainville in March of 1944.