Launch timings for attack on Cornwall and Dorsetshire

[Rob Stuart]

Glenn239 posted the following in another AHF thread. I think it should be in its own thread, so here we go:

… I have a couple questions for Rob Stuart, who is the Indian Ocean Raid expert.

In Osamu T's book on the Aichi Val, he mentions briefly a period of intensive training of two weeks in duration in the Celebes (Staring Bay?), right before the Indian Ocean Raid. All the lessons since Pearl Harbor were incorporated, culminating in a giant 2.5 hour exercise of all the air units of Soryu, Hiryu and Akagi over the fleet at anchor, (Shokaku and Zuikaku had just arrived, but did not participate). Is there any more information on this period, and what lessons were absorbed, and what the purpose of the training was?

Unfortunately I don’t yet have any detailed info on this training beyond what you’ve noted here yourself.

Secondly, before the bombing of Cornwall and Dorsetshire, the book mentions that Nagumo ordered Akagi, Hiryu and Soryu to emergency launch their Val squadrons against them. Akagi's commenced its launch about 20 minutes after the order went out, Hiryu's launched about 30 minutes later, Soryu's started launching "shortly' after Hiryu.

The 5 April timeline for this is as follows, in local time:

0600: The Colombo strike is launched – 53 B5Ns from CarDivs 1 and 2, 38 D3As from CarDiv5, 36 Zeros. This was the "Second Organization". The CarDiv1 and CarDiv2 D3As, armed with 250 kg ordinary bombs, and the CarDiv5 B5Ns, armed with torpedoes, are held back in case enemy ships are found at sea. This force was the "Third Organization". (The First Organization, which originally was to have been sent to attack Colombo, would have included all the B5Ns and all the D3As from all five carriers, launched in two deckloads.)

0600: Abukuma, Tone, Chikuma, Kongō, Haruna each launch one floatplane to search for enemy ships. (See Map 1 in “A Question of Estimates”, at https://www.usnwc.edu/getattachment/fb6 ... nce-D.aspx.)

0828: The attack on Colombo concludes and Fuchida recommends a second strike against Colombo be launched. “Request that second strike be made ready. Some ten transports are in the harbour. There is anti-aircraft fire. Enemy still has some aircraft. Dense clouds at 1,000 meters.”

0852: Nagumo orders Shokaku and Zuikaku to remove the torpedoes from their B5Ns and rearm them with 800 kg land bombs, for an attack on Colombo. A third of the D3As on the other three carriers were to change their 250kg “ordinary” bombs for 242kg land bombs.

0948: Re-arming of CarDiv5 B5Ns with bombs nearly complete.

1000 (received at 1005): Type 94 from Tone sends sighting report: "Sight what appears to be two enemy cruisers 268 degrees 150 nm from launch point. Course 160 degrees, speed 20 knots."

1023: Nagumo orders second wave aircraft to attack the British cruisers ”under 3rd Organization”. Shokaku and Zuikaku are to put the torpedoes back on their B5Ns.

1030: Nagumo to KdB: “Inform possible time to launch 3rd Organization (without Air Control Units)”.

1050: Abukuma’s Type 94 floatplane reports sighting two destroyers 250 degrees, 200 miles from its launch point.

1057: Hara to Nagumo: “Expect to complete preparation for launch at 1600 [1300 local]”.

1115 or 1118: Nagumo orders the second wave, without fighters, to start launching at 1200 to attack enemy cruisers.

1127: Nagumo decides that the Tone and Abukuma reports refer to the same ships and that they are destroyers, and signals to KdB as follows: “Previously mentioned cruisers are actually destroyers. Only launch [D3As] in 3rd Organization”.

1149: Akagi launches 17 D3A
1159: Hiryu launches 18 D3A
1203: Soryu launches 18 D3A

Questions-
How did Akagi launch it Val squadron only 20 minutes after the order came down?

Akagi did not launch its Val squadron only 20 minutes after the order came down. Nagumo’s order for the Third Organization to attack the newly discovered British ships was issued at 1023 and at 1115 or 1118 (I’m not sure which) Nagumo ordered the attack to be launched at 1200.

Why did Akagi launch 10 minutes before Hiryu?

Hiryu and Soryu launched at 1159 and 1203 because they had been ordered to launch at 1200. I do not know why Akagi launched 11 minutes early.

Glenn, you are misquoting Osamu’s book when you claim that Nagumo ordered Akagi, Hiryu and Soryu to “emergency launch” their D3As. It says no such thing, and the assumption you appear to be making that Nagumo simply ordered these aircraft to be launched as fast as possible, and that Akagi was able to launch in 20 minutes, is wrong. He maintained control of the launch process, and Akagi launched one hour and 26 minutes after receiving the order to get ready.

[glenn239]

Rob Stuart Unfortunately I don’t yet have any detailed info on this training beyond what you’ve noted here yourself.

Thanks. Looked to me like it was saying 1st Air Fleet reviewed its war experiences since December 1941 and updated its battle doctrine over the course of two weeks, and then tested it in a massive exercise involving the air groups of three carriers flying in unison over Staring Bay.

1115 or 1118: Nagumo orders the second wave, without fighters, to start launching at 1200 to attack enemy cruisers.

That answers my question – this 1115 order I don't see in the narrative on page 57. It mentions the 1127 order, which made it sound to me like Akagi first got the order at 1127 and commenced launch at 1149. But you’re saying Nagumo actually sent the order at 1115/18.

1149: Akagi launches 17 D3A
1159: Hiryu launches 18 D3A
1203: Soryu launches 18 D3A

Ok, so 14 minutes separation between the commencement of Akagi’s launch and that of Soryu's.

Glenn, you are misquoting Osamu’s book when you claim that Nagumo ordered Akagi, Hiryu and Soryu to “emergency launch” their D3As. It says no such thing, and the assumption you appear to be making that Nagumo simply ordered these aircraft to be launched as fast as possible, and that Akagi was able to launch in 20 minutes, is wrong.

Understood. I was making an assumption base from this,

“At 1127 hrs, therefore, Nagumo ordered just the dive bombers of the reserve force to take off. In response, 53 Type 99s winged their way toward the enemy ships, the pressure to launch quickly having left 16 of them still armed with 242kg land bombs from the first rearming order.”