This might sound like a naive question from an unscrupulous techie, but would biological warfare have been effective in naval combat in the Pacific theater? After all, a ship packed with 1000 or more sailors could allow infectious diseases to spread like fire. And unlike on land, there would be no risk of unwanted infection of civilians. So why not fire anthrax shells instead of the normal HE and AP? From what I've read, Japan didn't have any aerosol deliver capability (using fleas and porcelain shells - pretty low tech), nor mass produced biological agents. Or could it be that they purposely didn't use them militarily by principle? After all, they didn't use subs against enemy merchant shipping, thinking they would be an unworthy opponent. The US seemed to had no interest in biological weapons at the time. It seems since the allies had the ability to mass produce Penicillin, that would've discouraged Japan from using germs along with the threat of severe reprisals. But what about viruses which Penicillin won't stop? So if Japan or the US did manage to deploy anthrax shells or something similar, how would they defend against them? Issue gas masks to all AA personnel? Filter incoming air and maintain positive pressure inside the hull?