Definitely wasn't expecting the Japanese to try to directly hit the U.S. itself with chemical weapons. It's smart of Humphrey to avoid using sunbombs or superbombs, at least. I think it's safe to say that TL-191 has seen enough usage of them as it is.
The only thing I am curious about the reasoning for is this. Considering the casualties the US took in the First and Second Great Wars, you would think that the "American Society won't allow heavy losses" argument wouldn't apply to the US in TL-191. Then again, I wonder if the people that made that argument in OTL ever heard about the American Civil War.The debate is acrimonious, as the Imperial Japanese Navy’s leaders, led by Admiral Okada, question the need for a massive war with the Americans. Once again, Ishii stresses that the United States is politically fragmented, economically fragile, and without the tolerance for taking high casualties.