www.heritagedaily.com
According to testimony by veterans of the notorious Unit 731, in 1940 the Imperial Japanese Army Air Force dropped ceramic bombs containing fleas infected with the bubonic plague over Ningbo China. It was reported that over 100 people subsequently died of plague. The mastermind of this plan, Dr. Shiro Ishii showed a film of the operation to the imperial princes Tsuneyoshi Takeda and Takahito Mikasa.
https://www.nytimes.com/1995/03/17/world/unmasking-horror-a-special-report-japan-confronting-gruesome-war-atrocity.html?pagewanted=all&src=pm