Japanese ww2 weapons Americans feared the most...

Thanks for the tip. I also had not read of that important battle. One article, perhaps authored by someone whose first language is not English or else didn't bother to proof it, says this near the end:

The Battle of Kursk was the last major offensive they launched in Russia. The material damage done to the German Army was massive. The campaign was a strategic Soviet success, although they suffered more casualties. For the first time, a major German offensive had been stopped before achieving a breakthrough[22]. The defeat at Kursk was to prove in many ways more decisive than Stalingrad. Winston Churchill argued that the defeat at Kursk ‘heralded the downfall of the German army on the Eastern Front’[23]​

https://www.dailyhistory.org/Why_did_the_Germans_suffer_a_defeat_at_Kursk_in_1943?​

 

I didn't know about the aircraft transporting subs until I saw this post. It was an interesting read when I looked it up. The Japs had 18 of them in the planning stage but managed to produce only 5, I think. Their planned purpose was to sail to the Panama Canal and blow up the locks. They had a number of set backs which hampered their plans, but it would have been doable otherwise. At the end of the war, the U.S. had possession of the only one left. They studied it then destroyed it in order to deprive the Soviets access to the technology. No bigger submarine was produced until nuclear subs came about.