Japanese also shelled an oil field just outside of Santa Barbara and there's also the fire balloons that they launched and one balloon landed in Oregon, killing members of a church group. Their deaths are considered the only combat casualties to occur on U.S. soil during World War II.
ack-ack
Thanks for pointing those our, Ack-Ack! I do recall the fire balloons, but didn't remember there being any confirmed successes. I don't recall specifically reading about the shelling of the oil fields, but now that you mention it, it sounds familiar.
Regarding innovations in submarines, Germany definitely went the farthest, though the Japanese had some "firsts". Specifically, just weeks before the end of the war, Germany managed to deploy four submarines powered by Walther turbines. The Walther engine was first proposed, and initially began development, back in 1941. It was a semi-closed cycle engine that used 80%-pure hydrogen-peroxide, combined with diesel fuel, to drive the boat underwater; it still had conventional diesels for surface propulsion, and electric motors for slow and quiet underwater ops, as well. The hydrogen-peroxide was sprayed into a catalyst chamber, where the oxygen would dis-associate and provide the oxidizer for the combustion of the diesel fuel. Water was injected, creating steam, which drove the turbine. The byproducts were primarily water and CO2; the CO2 was vented directly to the sea. The Walther subs could attain sustained underwater speeds of 22-25 knots (as fast as the first nuke boats) for up to several hours. This meant the could move faster than the ASW forces could hunt them, and have the flexibility to move into attack positions of their choosing against convoys. Fortunately, the Walther subs attained operational status only in the last few weeks of the war, and none saw action. Like the Me-262, initial development was slow and halting; Hitler believed the war would be over before they could be brought to fruition. Also, the initial success of the U-boat campaign against the Allies contributed to the thought that the Walther boats were not going to be needed any time soon.
Back when I was in the Military, I did a paper about them, as part of an Engineering Communications course. My proposal was to build these as a complement the nuke fleet, for coastal patrols to guard against enemy boomers, since they could be built much cheaper, and would be operating close to support bases. I believe they would also be quieter than a nuke boat while operating their Walther turbines, at least at higher speeds, since one of the primary noise sources on a nuke boat are their water pumps. At the low reactor outputs used for slow speeds, convection circulation is sufficient to circulate the cooling water for the reactor; at high speeds, the pumps come on and add to the over all noise out put. A Walther sub does not use pumps, so it's engine plant would not be substantially more noisy at high speed than it is at low speed.
