Remembering that they still had more than 5,000 effective military aircraft and enough fuel reserves to send them out on one-way bombing missions. As well as fast, light coastal vessels that could accomplish much the same thing in the event of any D-day crush of landing craft, especially at night. And at least enough hand grenades and mortar rounds that every *civilian* man, woman and child over the age of five years would have one.
There was once a writeup at “http://www.webwizpro.com/1945InvasionofJapan.html";, no longer there, which detailed what an invasion of Japan would likely have looked like.
It was a long litany of melted anti-aircraft gun barrels, swarms of kamakazi torpedo boats, cave-emplaced artillery, and millions of civilians with pointy sticks.