Submarine I-401, largest of WWII submarines

Hello, Mac
Came across a little quiz question in looking through your submarine warfare site a while back regarding the largest of WWII subs, equipped with two aircraft and able to sail around the world 1 1/2 times. Figured it had to have been the Japanese, though I likely heard of it several years ago and just didn't recall. It seemed fitting of them to have conceived such a grand folly. I suppose it might have made a good merchant raider, but oh how vulnerable it would have been during launch and recovery of aircraft! What would they do should a sudden storm have come up while their planes were aloft? And imagine the echo of a four hundred foot long sub to a destroyer's active sonar, not to mention the passive sonar signature such a mammoth would no doubt have generated, hangars and all, while underway submerged. Definitely something that would have had to operate well away from surface combatants, against merchant shipping or to harass unsuspecting coastal targets. Waste of their precious steel, fuel and men, I say, especially as they didn't even commission until near the close of the war.

In any case, here's a link to the wreck of one that was scuttled off Hawaii in '46, I think, after we had examined it and to keep it from the Russians: 




I agree the concept of the I 400 class of Japanese submarine was way out. Landing and recovering their aircraft could be a hazardous operation.

The Japanese I class that carried the midgets to attack Sydney Harbour in May/June of 1942, carried either an aircraft or a midget on their casing.

One of their seaplanes flew over Sydney and returned safely to her mother sub, only to crash alongside in rough weather, and sink, but the crew were recovered.

Of course as a precursor, we saw the advent of the French Submarine Surcouf, who had an 8 inch turret on her deck, and a seaplane hangar aft.

All in all, a rather ugly beast that went missing in unusual circumstances  in WW2, and her wreck still eludes the wreck hunters.

Good to hear from you.


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