This Cracked article claims that Japanese soldiers in WWII would eat prisoners of war.
The article claims that there were a number of documented cases of Japanese soldiers engaging in cannibalism:
The document helped Tanaka uncover over 100 hushed-up cases of confirmed cannibalism by the Japanese Imperial Army, with them eating Australian and Indian soldiers, and even Asian citizens.
It further claims that these cases were known by higher command and sometimes even supported:
On many of these picnics, the soldiers weren't even starving. Instead, cannibalism was practiced under the supervision of the commanding officer as a team-building exercise, meant to strengthen the warrior spirit and consolidate interpersonal bonds
Is there evidence to prove these claims?
The above link is for a comedy website, but one that claims to provide accurate information in a comedic fashion. As the article claims to be reporting on true information, and it is known to have a large base of viewers, I believe this would qualify as a notable claim.