I know that this topic was roughly handled a few months ago in the "Rising Sun Over Hawaii ..." thread here but I'd like to re-visit it if anyone else is interested ?
I'd like your comments/suggestions for a Japanese blockship design suitable for an alternative history Pearl Harbor attempt on Dec.7'41.
Historically the Japanese received pre-war (but post-embargo) US permission to send 4 liners across the Pacific as repatriation vessels to return American and Japanese citizens to their home countries during that time of crisis. The 4th and last Japanese vessel scheduled to make that Yokohama-Honolulu-San Francisco crossing was the 17,000 ton 21 knot NYK cargo-liner Tatuta (also spelled Tatsuta) Maru. Which can be seen at http://www.west-point.org/family/japanese-pow/PhotoFile/Tatsuta_maru.jpg
Historically the Japanese wished her scheduled to arrive outside Honolulu at 0700 on Dec.9'41 as a way to keep the Americans there relaxed. Who would expect an attack on Oahu just before a big civilian liner was scheduled to arrive ? In fact she did depart Yokohama on schedule, with paying US passengers, but turned around in mid-Pacific at midnight on Dec.6-7'41 so as to avoid the Kido Butai's Dec.7th air attack on Pearl Harbor. Gordon Prange's book, "At Dawn We Slept" presents these details.
I would like to explore, here, the "what if" impact of the Japanese instead requesting (and being granted) US permission for an 0700 Dec.7'41 arrival outside of Honolulu for a (disguised) 585' long Tatuta Maru (my blockship). This being my point of departure from the origianal timeline.
The Pearl Harbor entrance channel and it's surrounding restricted sea zone had been historically guarded 24/7 since 1939 by a peacetime gateguard destroyer. That morning the USS Ward followed a 15 knot patrol box circuit box of some 2 miles by 2 miles thru which travelled a fairly steady stream of smaller USN vessels including transports, garbage scows and minesweepers. So many and so regularly in fact that the twin anti-submarine nets strung across that entrance were usually left open between 0500 and 1900, the daylight hours, every peacetime day.
The channel dimensions at the nets were 700' wide by 72' deep which quickly shallowed to a constant dredged depth of 40' thru the entire channel leading into Pearl Harbor itself.
Only one US Coastal Artillery battery, consisting of one 60" searchlight on a 50' tower and 4x155mm GPF guns stood on Sand Island, at Honolulu Harbor, watching over the entrances to both harbors, simultaneously. Although the PH entrance was some 6 miles away. This sandbag protected "Examination Battery" was also guarded against air attack by an emplaced (but not usually manned) US battery of 4x3" AA guns, also located on the Sand Island Military Reserve.
I'd like your suggestions on how the Tatuta Maru could have been fitted out by the Japanese to become Adm. Kimmel's worst nightmare ? And any operational details that you'd care to suggest as well. Please remember that drydock time in Japan at this time was at a premium as war approached. Also that the overflight of Tatuta Maru by USN PBY long ranged air recon. aircraft, as she approached Oahu, was nearly guaranteed. As had been the case for the three previous historical repatriation trans-Pacific cargo-liner trips.
Just to make the scenario more plausible I would also propose the alteration of the historical orders given to the 5 Japanese minisubs
present that morning. Rather than attempting to sneak into Pearl Harbor itself, they would instead be ordered to torpedo the patrolling gateguard US destroyer, USS Ward, by 0730 ambush. Twice, to insure that her torpedoes could not offend the now charging Tatuta Maru.
The Japanese consular spy, Yoshikawa, could have observed the gateguard's regular patrol box and reported it's habits to Tokyo. With the distraction of having to stop to place a Honolulu Harbor pilot and a US Marine inspection team aboard her via the captain's gig, I'd doubt that the Ward would be watching for nor be able to evade the Japanese secret minisubs that were completely unknown to the US at the time. Any/all minisubs still having torpedoes after Ward was hit twice, would follow my Tatuta Maru into the PH entrance channel and takeup ambush positions around her, on the bottom there. Any US warship attempting to slowly squeeze past that anchored and scuttled blockship might thus join her in further jamming that channel.
How would you (and indeed could you) prevent my corking up of Pearl Harbor with the Tatuta Maru on Dec.7'41 ? And could I do so without giving away the remainder of the historical Japanese 0755 surprise air attack ?