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Introduction

The IJN followed quite standard British construction methods (unsurprisingly). During the construction of these ships, they experienced delays as Russ has noted due to main engines and the revolutionary armament. In addition, there were significant changes to the ships also accommodated within the construction process. The Type B DD was not originally designed with the quadruple torpedo mount. There was a debate inside the IJN about the ship as it was originally designed with a purely defensive role as an AA DD. So the design was changed at the last minute (after long lead items were ordered) and the first 6 ships laid down.

Shortly after completion in OTL, the increasing Allied SS threat saw their stern minesweeping gear removed and replaced with 4 DC throwers and 54 DC. This is significant to FFO as it shows that the IJN was well able to make smaller changes like this 'on the fly', just as the RN was.

The class was fitted with TWO Type 94 Directors for the main guns. According to Fascicle O-1, Target O-30 USNTMJ Report 'Japanese Anti-Aircraft Fore Control', the Type 94 system "…was similar to and can be compared with the U.S. Mark 37 system". (See report pp13-17)

FFO

There is one thing good about working out the IJN's responses in FFO. They are, as they were in OTL, logical.

OK, so in FFO we have the Kondo Report, which says 'our AA is inadequate as is our A/S'. This class already had ASDIC, of course, so we can assume that replacing the stern minesweeping gear with 2 DC racks and 4 DC thowers (78 DC) will be done prior to completion.

Their OTL light AA armament was two twin 25mm amidships with a Type 95 short range HA director (Shageki Sochi). This was the only system associated with the IJN's remote-controlled mount, the 25mm triple. As this RC mount is being used in FFO as a twin 37mm mount using German guns, we can assume at this early stage of the war that this director will be used.

This director was used with 2-3 twin or triple 25mm IJN standard Ward-Leonard Remote Power Control mountings.

Therefore, with no modification whatsoever from OTL, the ships could be completed with two twin 37mm mounts amidships using Type 95 Director and two twin 37mm fitted Ward-Leonard mounts.

But this will not be adequate after the Kondo Report. What that report also does is to increase the importance of these ships. I cannot see how any delays would be countenanced in their completion at all - quite the opposite, in fact. They just became much more urgent. This, of course, also explains them getting 37mm and more AA overall.

The design had a searchlight on a plinth between the mainmast and the TT. It is a simple matter to place another twin 37mm on that plinth. This gives the Type 95 director amidships three RC mounts to control. It is designed for that, so we again have no problems or delays.

The demand for 37mm is such that an initial fit of 3 x 2 mounts appears to be adequate. More will probably not be available at this time, but will be planned for the future. Meanwhile, 25mm will have to do.

The easy things first. Adding 8 x 1 single manually-operated 25mm (4 forward and 4 aft) is simple.

The next step is to add the stands and director (another Type 95) for three triple 25mm RC mounts. The bandstands are easily located one on each side of the bridge and one two decks high on the bridge face to cover the bow arc. With the priority these ships will attract, these will also be twin 37mm RC mounts, but probably not in 1942. They will probably only hold manually operated triple 25mm until early 1943.

The additional Type 95 director can only be placed on a foremast platform. This will require the mast to be altered from the original light tripod design to the heavy DD tripod seen on these ships in 1943. This design has a masthead platform and will be able to take the Type 95.

I actually think that it is a little too early for German-style DCT for these ships. I cannot see the production numbers being available yet and think that German HA FC to replace Type 95 will still be in land range and target ship testing for 1942.

Radars: Jacques noted that : "…the prototype installation of the FFO Mk2 Mod3 radar similar to the German FuMo 24 with a 6m x 2m manually rotated antenna giving a 15nm range on ships and a 25nm range on medium-sized aircraft at 5,000m altitude. This set was mostly developed for destroyers and cruisers)."

I agree. There is only one place to put this on these ships. It has to do on the mainmast. That makes the mainmast as designed inadequate. Fortunately, there is ample space there for a heavier vertical tripod with a platform to take this radar.

Our modifications then are:

- four additional IJN standard light AA bandstands

- three 25mm triple mount with twin 37mm

- three 25mm triple (probably manual)

- eight single 25mm manual

- one Type 95 director

- heavier mainmast to be fitted

- heavier foremast to be fitted

- one FFO Mk2 Mod 3

- four DC throwers

- two DC racks

- removal of stern minesweeping gear

In view of this, I can see no reason why this work cannot be performed before the completion of the ships. In the IJN as in the RN, trials of new equipment was the role of shore establishments and trials ships fitted with the equipment, not operational warships required by the Fleet.

Cheers: Mark

FYI, TROMs below

Akizuki

LD - 30 Jul 40

Launched - 2 July 41

Completed - 13 Jun 42

11 June 1942:
Completed at Maizuru. Ship's captain: Commander Koga Yasuji (prev. C.O. YAMAGUMO).

15 June:
Departed Kure, escorting ZUIKAKU to Northern Area in expectation of U.S. counterattack in the Aleutians.

29 June-18 July:
Escorted liner KAMAKURA MARU from Yokosuka to Makassar (6-10 July) and back.

13-21 August:
Escorted ammunition ship NARUTO MARU from Yokosuka via Kavieng to Rabaul.

24 August: Battle of the Eastern Solomons
Joined escort of Admiral Nagumo's Striking Force.

September:
Escorted fleet patrolling out of Truk north of the Solomons.

27-29 September:
Steamed from Truk to Shortlands. On 29 September weathered attack by B-17s near Buka without damage.

3 October:
Out of Shortlands to assist NISSHIN against U.S. aircraft.

7 October:
Escorted NISSHIN on troop transport run to Guadalcanal, aborted due to weather; on same date, assigned to Desdiv 61, Desron 10, Third Fleet.

8 October:
Escorted NISSHIN on troop transport run to Guadalcanal.

11 October:
Escorted NISSHIN and CHITOSE on troop transport run to Guadalcanal.

12-16 October:
Became flagship of Comdesron 4 (Rear Admiral Takama Tamotsu), then led escort of troop convoy from Shortlands to Guadalcanal and back.

17 October:
Led troop transport run to Guadalcanal (cover).

25 October:
Led gunfire support mission to Guadalcanal (Hyakutake offensive), aborted. Assisted in rescue of survivors from bombed YURA. Medium damage: when near-missed by U.S. aircraft and left temporarily unnavigable due to damage in engineering spaces. Admiral Takama transferred to MURASAME.

27-31 October:
Alongside repair ship HAKKAI MARU at Rabaul.

1-6 November:
Escorted SHOKAKU and CHIKUMA from Truk to Japan, then docked at Yokosuka for repairs.

16 December:
Repairs completed.

31 December 1942-4 January 1943:
Escorted ZUIKAKU from Yokosuka to Truk.

Teruzuki

LD - 13 Nov 40

Launched - 21 Nov 41

Completed - 31 Aug 42

31 August 1942:
Completed at Nagasaki. Ship's captain: Commander Orita Tsuneo (prev. C.O. HAMAKAZE).

7 October:
Assigned to Desdiv 61, Desron 10, Third Fleet.

10-14 October:
Steamed from Yokosuka to Truk, then joined fleet at sea north of the Solomons.

26-27 October: Battle of Santa Cruz
Escorted Admiral Nagumo's Striking Force; later escorted damaged ZUIHO away from area. Minor damage: when near-missed by bomb from PBY: slight hull damage and seven dead.

29 October:
Arrived alongside AKASHI at Truk for repairs.

12-13 November: First Naval Battle of Guadalcanal
Escorted Admiral Abe's Bombardment Force. Claimed hits on all seven enemy ships engaged, including one sinking. Assisted crippled HIEI during daylight hours of 13 November.

14-15 November: Second Naval Battle of Guadalcanal
Joined Admiral Kondo's Emergency Bombardment Force, then with ASAGUMO provided close cover to the heavy ships. Assisted crippled KIRISHIMA and helped remove survivors.

18 November-1 December:
Arrived Truk, then became flagship of Comdesron 10 (Rear Admiral Kimura Susumu) until arrival at Truk of AGANO.

3 December:
Minor damage: clipped reef at Truk.

5-7 December:
Steamed from Truk to the Shortlands, then became flagship of Comdesron 2 (Rear Admiral Tanaka Raizo).

11-12 December:
Led supply-drum transport run to Guadalcanal (cover). Sunk: while patrolling close to shore at low speed, was attacked by U.S. PT-37 and PT-40, torpedoed and left dead in the water. Fires spread over the next three hours until reaching depth-charges, resulting explosions sinking the ship. NAGANAMI removed Admiral Tanaka and 56 others, ARASHI rescued 140 survivors and another 156 reached Kamimbo (Guadalcanal) in boats; Commander Orita (later Comdesdiv 32) among the survivors. NOTE: While all accounts state clearly that TERUZUKI sank off Guadalcanal, most official sources list her sinking coordinates as 7-50 S, 157-30 E -- or 20 miles NE of Kolombangara! Actual sinking coordinates are apparently unavailable.

Imah, I simply do not see it. There is simply nothing structural to cause a delay to an already delayed construction timetable. These were the sort of things which were done as minor add-ons to Allied DD and frigates in normal harbour turn-around cycles (not refits). Here the ships are in the building yard, not alongside in Liverpool waiting for another convoy.

Let's look at it:

- four additional IJN standard light AA bandstands: fabricated in a shop of welded flat panels (these are all flatwork). A small crane to lift and emplace, then it's a quick welding job. The wiring would only take a couple of days, and that's the hard bit.

- three 25mm triple mount with twin 37mm: Not a yard issue, the mount is an IJN standard fitting several days to fit, connect and test.

- three 25mm triple (probably manual): ship from stores

- eight single 25mm manual; perhaps half a day all up, assuming two welders?

- one Type 95 director: again a standard stores item

- heavier mainmast to be fitted: One complex item here and one has to be manufactured and fitted anyway. No delay is really possible.

- heavier foremast to be fitted: One complex item here and one has to be manufactured and fitted anyway. No delay is really possible.

- one FFO Mk2 Mod 3: like the AA guns, assumed to be a standard production item

- four DC throwers: A day's work or so

- two DC racks: A day's work or so

- removal of stern minesweeping gear: A day's work or so

The thing is from the yard perspective that all of this is just normal minor fitout work and all of it can occur concurrently with any other activity being done on the ships because it is all upper-decks work.

There is no need at all to remove the torpedoes or the reloads.

But what will really take time is working things out to have real operational ships (foreign gun AND foreign AA director).

What foreign gun director? As I have explained (and I can give sources for their systems), at this early stage, they'd use the standard IJN Type 95 AA director with standard IJN Ward-Leonard triple 25mm mountings and merely replace the triple 25mm with twin 37mm. That is quick and easy. It will take longer to develop and test a new director (which they will need, Type 95 is basic). I cannot see this appearing before about March 1943 on ANY IJN ship except whatever vessel they are using for sea trials for light gun systems. The German-style light AA director would still be in trials in late 1942. In any case, all that sort of work is done at shore firing and test ranges. The IJN version of Portdown was located on the shores of Tokyo Bay.

Cheers: Mark