M o d e l W a r s h i p s . c o m Imperial Japanese Navy – Mogami Class Light Cruiser MIKUMA -

Birth, history and operational service

After the building of the IJN Atago class heavy cruiser “MAYA”, that I ended in 2005 after a three years work, I concentrated my attention on a particular unit of the Mogami class, the “MIKUMA”, which life and operational service were much shorter than the other twin vessels of the same class, the Mogami, Suzuya and Kumano.
The Mikuma, whose project was based on an original 10.000 tons displacement design, was a first class cruiser, according to the classification standards used by the Imperial Japanese Navy since 1898, which considered this kind of vessels with a displacement of more than 7.000 tons as first class cruisers, while units with a lower displacement were rated as second class cruisers.
In 1931, when Mikuma and Mogami were laid down, a radical change touched the above mentioned classification standards, which, by then, gave up the displacement criterium and determined the cruisers according to the their main guns caliber.
Consequently, the new criteria fixed the cruisers in two classes: heavy cruisers, armed with main guns caliber bigger than 155 mm and light cruiser, with heavy guns up to 155 mm caliber.
So, the Mikuma was defined as a light cruiser, in spite of her 10.000 tons displacement that would have determined her as a first class cruiser.
The birth of the Mogami class cruisers was well known and had well definite reasons. It was the right reply to the Imperial Japanese Navy General Staff’s necessity of verifying if this kind of cruisers, partially different from the other cruiser classes, could have accomplished the tasks that pertained vessels that had a heavier displacement and heavier guns, as, for example, the Myoko class or the newest Atago class, with a total displacement for every unit of both classes of about 15.000 tons and armed with ten 203 mm guns.
The technological development on metals and Japanese military shipyard building systems, with a particular reference to the light alloys and electric welding, convinced the IJN General Staff that the saving of weight obtained with the employment of new technologies and industrial processes could be used for the fitting up of a larger number of guns then the previous cruisers classes, especially if the Mogami class project staff would have concentrated his attention on the new 155 mm gun.
The previous Washington Treaty of 1922 and the following London Naval Treaty of 1930, to which Japan and the other main countries agreed over these years, determined that there was a maximum of tonnage for every category of military vessels owned by every country's navy and defined very precise technical limits to the building, displacement and armament standards of the combat ships.
As concerning the cruisers, the Treaties established a maximum displacement for every unit of 10.000 tons and not more than ten 203 mm guns.
So that, the need of the Imperial Japanese Navy of building vessels that must be on the whole superior to the contemporary Allied ships, always respecting the limits of the Treaties, was supported and got stronger by Isoroku Yamamoto, one of the best navy commanders and strategists than Japan had ever had, who brought a new and revolutionary military doctrine.
As future commander of the Combined Fleet, between the end of the ‘20 and the beginning of the ’30, Isoroku Yamamoto believed that the growing use of an embarked air force in a large number of aircraft carriers, with deep attack and naval forces covering tasks, together with the short distance naval engagement principle, were the basis of his new naval war theory.

From this point of view, the new 155 mm gun (6.1 in), lighter than the 203 mm, could have assured, if compared to the 8 in gun, a larger number of guns fitted in the ships, respecting the displacement limits of the Treaties; furthermore, its effective firing rate of 5 shells per minute was far superior to the 2/3 shells per minute firing rate of the 203 mm gun; then, if we also consider that the weight of the triple 155 mm turrets full salvo was the same or often superior to that of the double 203 mm turrets (the Mikuma, with her 15 155 mm 60 cal 3 Nendo Shiki guns, could rain on the enemy ship a full salvo total weight of about 4.200 kilos of explosive and metal per minute, with a firing rate of 75 shells per minute, while the heavier Atago class, for example, with its 10 203 mm guns, could rain a full salvo total weight of about 3.780 kilos per minute and had a firing rate of 30 shells per minute), it’s quite easy to understand that the birth of the Mogami class could be supported by good presuppositions.
The 155 mm gun, notwithstanding its lower weight of the single shell and of the single explosive charge and lower maximum range than the 203 mm, could actually counter-balance its supposed inferiority with a higher firing rate and, consequently, with a superior fire volume; this was absolutely useful for the short distance naval engagement that was theorized by Yamamoto, who always tried to avoid the long distance naval battles, in which allied ships could have been superior.
Furthermore, the fact that Japan certainly exhausted the possibility of launching more heavy cruisers, for the imposed naval limits, put a strong pressure on the IJN General Staff concerning the decision of building the four light cruiser of the Mogami class.
But the new Yamamoto’s doctrine on cruisers employment, soon led the IJN General Staff to realize that the displacement limits of the Treaties would be easily exceeded if the new ships would have assured the performance expected by the Navy; a true proof of this was the total displacement of about 14.000 tons of the Mikuma in 1939, when the powers involved in the forthcoming 2nd world war had still put the observance of the Treaty limits away.
With a length of about 200 metres and a beam of about 20 mt, the Mikuma was a heavy armed cruiser, with a beautiful line, a huge hull and little superstructures, if compared to the other Japanese cruisers design of that era.
It was a fast ship and its AA armament was composed by four 127 mm high angle gun in twin mountings, located in the center of the ship and four type 96 25 mm twin MG, located in the center superstructure that enclosed the big funnel, fitted for turning the smoke out that was produced by 10 Kampon boilers, with a maximum power of 152.000 shp.
Another two 13 mm twin MG were located in a platform that was in the front part of the main tower, just behind the 155 mm turret no. 3.
Furthermore, the Mikuma was armed with twelve 610 mm (24 in) torpedo tubes, in triple mountings, mounted on the upper deck at the after end of the superstructure, fitted for firing the powerful oxygen-propelled “Long Lance” torpedoes, one of the worst certitudes that allied ships must face during the Pacific War.
The extensive use of the light alloy and electric welding, instead of the riveted plates, gave the opportunity of building lighter ships, allowing, in consequence, the fitting of a higher number of guns; nevertheless, this “building lightening” that was pushed over the limits of an acceptable and unavoidable risk margin, caused such a structural weakness that after the “4th Fleet Incident” occurred on September 1935, when a huge typhoon struck the 4th Fleet with Mikuma and Mogami also, the heavy damages caused by the strong winds and very high wakes to the ships structures, led the IJN General Staff to completely revise all the ships building projects and building process, with the main aim of recovering the structural safety of the ships.

After the sea trials, Mikuma and Mogami showed some serious structural deficiency; the wrong weights subdivision, with an excess of weight coming from the superstructures and the armament compared with the hull and machinery, caused a rise of the barycentric height and a lacking in athwartship stability; in consequence, there was a dramatic rolling and the ship couldn’t be a good shooting platform.
Furthermore, during the first 155 mm firing tests, the strong vibrations and recoils caused by the 155 mm broadsides, caused some hull distortions and infiltrations of water in the welded plates. Then, also the heavy damages caused by the typhoon of September 1935, finally led the Mikuma to enter the Kure dockyard for an heavy reconstruction and refit that took from April 1936 to October 1937.
The interior main structures were strengthened and the welded plates were replaced by riveted plates; then some plates were added on the bottom of the keel and the 127 mm AA gun deck was reinforced near the gun turrets; furthermore, the reconstruction eliminated the connections between the barbettes of the no. 3 and no. 4 155 mm gun turrets and the 127 mm gun deck, to prevent the effect of the hull distortion caused by the 155 mm gun firing. Then, new bigger bulges were added over the old ones, so that both beam and displacement increased, together with a lowering of the barycentric height that caused an improvement of the athwartship stability; then, the main mast was also lowered.
In 1937, the heavily modified Mikuma was definitively commissioned and formed the famous 7th Cruiser Division of the Imperial Japanese Navy together with the Mogami, Suzuya and Kumano.
The apparition of the four Mogami class units was not a real surprise for the western powers, that actually were informed about the strategic plans of Japan; their answers were not to be expected so long.
In fact, Great Britain drew up the eight light cruisers of the Southampton class, while the United States commissioned the nine Brooklyn class light cruisers, both classes armed with 155 mm guns.
This difference in navy forces, 17 vs 4, led the IJN General Staff to partially revise the employment doctrine of light cruisers; this doctrine did not lose its general validity, but it would have been revised in the light of this new and unfavourable (for Japan) intercourse of the naval forces.
For this and other reasons, in 1939 the IJN General Staff decided to modify the four Mogami again, fitting the 203 mm guns instead of the 155 mm guns and turning them into heavy cruisers, with the main aim of counterbalancing the cropped up inferiority in numbers with a heavier power of the single Japanese unit than the enemy unit.
Regarding the operational service, in 1937 – 1938 the Mikuma was incorporated in the 7th Cruisers Division and used in Chinese waters during the Chino-Japanese war.
After the great reconstruction of 1939 and the consequently modifying as an heavy cruiser, the Mikuma was used in Indo-China in 1941, to put pressure to the Vichy France government in that territory. In July of the same year, the Mikuma was supporting the advancing of the Japanese troops in Indo-China, fighting against the Vichy France army, but this was not a bloody combat because of their political opportunism dictated by the fact that they had a common allied, the Hitler’s Germany.
After the raid against the US naval base of Pearl Harbour of December 7th 1941, the Mikuma was employed with the 7th Cruisers Division to support the Japanese landing forces in Malaya, Borneo, Sumatra, Java, and Andamane Islands.
Between the 28th of February and 1st of March 1942, the Mikuma and Mogami sank the US cruiser USS Houston and the Australian cruiser Perth, off Batavia, soon after the important Japanese victory in the battle of Java See.
On April 1942, the Mikuma took part in the Japanese naval attack force against the allied merchant ships in the Indian Ocean, and after a short period in the dockyard for a little refit, in May 1942 she was ready to fight again.
On June 1942 she took part in the battle of Midway, where the Mikuma saw her end of life.
The 29th of May of the same year, the 7th Cruisers Division was ordered to leave from Guam to escort the Japanese convoys that would have landed in the isle of Midway; the 5th of June the Mikuma was ordered to shell the isle for supporting Japanese landing troops, but soon the order was cancelled and the Mikuma, together with Mogami, retreated to their base.
During the return voyage, the Japanese naval force was intercepted by the US submarine USS Tambour, and during the agitated Japanese diverting actions to avoid the torpedoes danger, the Mogami and Mikuma collided, with heavy damages on the Mikuma.
In spite of this, the two cruisers went on their way at a low speed, so that they soon were sighted by the dive-bombers and torpedo-bombers from the US carriers Yorktown, Hornet and Enterprise.
The attack arrived soon and was deadly for the Mikuma: hit by bombs and by a US plane that crushed near the aft no. 4 155 mm gun turret, the cruiser soon became a burning wreckage and sank the night of June 6th 1942, about 500 miles west-north-west of Midway, bringing lots of men to the bottom with her.

Building the kit

The Mikuma’s kit is the classic 1:700 Tamiya; the quality standard of the Japanese firm is full confirmed by this kit, also if it’s not at the same level as the Rodney’s and Nelson’s kits, the Hood’s kit or the Prinz Eugen’s kit, that were unbelievable detailed.
The model can be built just out of the box, without adding extra parts and the result could be very interesting, due to the high quality of the Tamiya’s kit.
But if you want to build something special, something more than a simple model, at the cost of growing exceedingly the building time, the scratch-building of all or quite all the model is the only way out.
Consequently, the Mikuma also (as for other models of mine, like the IJN heavy cruiser Maya of 2005) is practically scratch-built, preserving only a few parts of the kit: the hull and some parts of the main tower and funnel.
Once I have verified the accurate measures in 1:700 and the right hull shape, comparing them to some drawings of the vessel, I detailed it by using cut tape (the “Magic-Invisible” of the 3M) to create the different belts of steel side plates.
After that, I drilled all the port-holes, I added the outer screws markers, the ladder and 9 mt launches davits, the leadsman’s platforms and sounding platforms, the scupper pipes; then, I cut away all the details of the main and 127 mm guns decks (reels, mushroom vents, hatches, watertight doors, etc…) for substituting them later with photoetching and scratch-built parts.
Then I closed the hawse pipes with putty because of their wrong shape and position and I made them again with the right shape and position; after that, I drilled the decks where I cut the old mushroom vents, so that I could insert the brass parts from Clipper Models.
The hull was then airbrushed with the White Ensign Model WEMCC IJN 02 – IJN Kure Grey – as Snyder & Short said precisely about the Mikuma in her 1938 configuration. As soon as the color has dried, I did a little dry-brush on the hull, with a vertical movement, using first a medium-dark grey, then the Humbrol 64 (light grey) and, for last, the Humbrol 147 (a very light grey).
This is a very delicate phase of the work: if the dry-brush is too evident (too evident means that the edges of the ship parts are too bright), the model becomes absolutely unreal. When the hull weathering was finished, I masked all the hull to cover the work I’ve done and I airbrushed the decks with the WEMCC IJN 10 – IJN Linoleum – that was later dry-brushed with the Humbrol HM 1 “8th Army Desert Yellow”, then the Humbrol 121 (a very light brown) and then the Humbrol 24 (yellow).
Using the last color has allowed to put in evidence the very thin strips that Tamiya has drawn onto the deck; these strips simulates the thin brass strips of the real ship, which were the support of linoleum joints.
Then I added the Clipper Models’ Mushroom vents, the reels, anchors, watertight doors, deck hatches and ammunition boxes from Lion Roar; the 127 mm HA gun loading exercise machine was completely scratch-built; it was located, on the Mikuma, just after the no. 5 155 mm gun turret.
Then I added a very very little drop of Microscale’s Micro Kristal Klear inside every port-holes that I have drilled on the hull; after the Kristal Klear has dried, it simulated the glass very well.
As soon as I finished the hull (but there were some little details that I haven’t added yet), I started to work on the remaining three main parts: 1) the main tower bridge structure, composed by seven levels in the real ship, and the foremast, 2) the central structure, used as a platform for the 25 mm aa machine guns, and the big funnel, 3) the aft structure, with the mainmast.

Starting from the Tamiya’s original part of the main tower bridge structure, I cut all the wrong parts and I scratch-built the compass bridge deck, the upper bridge and fire command platform; the windows on the compass bridge deck were simulated by cutting a piece of hanging ladder of the right measure, to which I glued a thin stripe of transparent acetate (the material that in Italy we find usually in the brand new shirt boxes). Also the frontal platform for the 13 mm aa machine guns, the signal platforms, the type 95 director tower, the type 94 rangefinder tower with its 6 mt rangefinder, the semaphore signal stations, the 12 cm and 18 cm binoculars, the type 92 torpedo fire command panels, the type 91 model 3 torpedo directors, the type 94 searchlight control installations, the two type 91 high angle director towers, were all scratch-built, as for the remaining details of the main tower bridge structure that would be impossible to reckon up one by one.
The engine room ventilation cowls (13) have been made by using the Gold Medal Models photoetched nets for the modern ships, cut and shaped in the right way.
The foremast was made by using the photoetched part from Pit-Road, to which I added the anemometers, the RDF room with its platform and ladder, the RDF antenna, the signal lights (made by a very little drop of Kristal Klear), the yardarm and all the other little details.
As soon as I’ve finished the construction of the main tower bridge structure and the foremast, I added the two photoetched 13 mm aa twin machine guns (Lion Roar), the ammunition boxes, the searchlights, the binoculars, the rangefinder and all the railings.
After that, I started to build the funnel and the central structure, where the light artillery, the four 25 mm aa twin machine guns, was located.
The big funnel was composed by two separate parts that joined together on the top of the funnel, just under the cap (as other Japanese vessels of that period); the shape of the kit funnel was wrong, and the engine room ventilation cowls located on its base were wrong too. For this reason, I had to scratch-build all the low part of the funnel, the ventilation cowls and all the auxiliary and external pipes (12), so that they were not jointly liable with the funnel but, on the contrary, they had a true 3D effect that was unknown before.
Then I added al the photoetched “walkways” on the funnel, the two sirens, the protection grill on the funnel cap (made by copper wires) and the long hanging ladder that started from the base of the funnel, just behind the main tower bridge structure and arrived to the funnel cap.
As soon as I finished the funnel, I completely re-built the structure around it for the 25 mm aa machine guns, the passage connecting trenches and ladders from this structure to the funnel and the deck and the three circular platforms with braces structure for the 110 cm searchlight. Then I glued the 25 mm mg with ammunition boxes (all from Lion Roar), with the hanging ladders and railings.
Then I glued this section to the hull, being careful to the exact alignment between the first and the second section and also between the two sections and the lengthwise half line of the deck.
The third section, that one of the aft structure and mainmast, was scratch-built all the same; the reason was because the kit aft structure was wrong, as concerning the shape of it (or better, the shape was right for the Mikuma in 1942, at her loss date, but as I want to depict the cruiser in 1938, the shape of this structure could have been quite different), and because the kit mainmast was out of scale and too poor.

For the mast I used different diameter brass rods; then all the small details were added, as concerning the anemometers, navigation lamps, platforms, ladders, two small searchlights, the crane for the seaplanes and for the boats (from Lion Roar) and the rotation mechanism of the crane around its central pivot, played by the mast. This mechanism was composed, in the real ship, by a big cog-wheel that was moved by another more little cog-wheel; this last was connected, by a vertical shaft, to an engine that was located in the aft structure.
As I had lots of very strange spare parts in my private “spare parts bank”, I found out some extra-little watches gears that were absolutely right to represent the cog-wheels mentioned above.
Then I glued the aft structure and the mainmast to the deck and checked the exact alignment of this section to the previous ones; as soon as I did it, I started to build the 155 mm gun turrets, made by resin starting from a modified master, with the brass barrels from Clipper Models, the 127 mm HA guns from Lion Roar, heavily modified with scratch-built parts (the 127 mm guns turrets are four, and every turret is composed by 54 parts), the cutters and motor boats, the three embarked seaplanes (two Dave and one Alf) with connecting rods between the wings, seats, etc.., the Kure type 2 model 3 catapults, the aircraft deck rails and turntable, the railings, the stanchions with rigging, the jack staff and ensign staff and so on.
Then, some dozens of wooden boxes full of provisions for the crew and materials for the on board living have been added together with about 300 photoetched men (from Eduard).
If in my previous model, the heavy cruiser “Maya”, I attended about 3500 parts for the total construction, for the Mikuma I couldn’t remember at all, because at a certain time of the model building, I had no wish to count all the pieces; but I’m sure to have exceeded that figure, because there was much work and scratch-building on the Mikuma than the Maya..
I know it’s crazy or impossible to understand, but it’s the only way, to me, to amuse myself when making a ship model!
I depicted the Mikuma as it was in August 1938, during her staying in the Bungo Strait and Ise Wan areas.

Acknowledgements

I would like to express my sincere thanks to those who have helped me both directly and indirectly in collecting materials and information for this model and to the friends who have offered advices on construction process.
I’m especially grateful to Mario Papa, Alberto Maestri and Luca Tarpani, from Perugia (Italy), Giampiero Galeotti (Regiamarinamas) from Rome (Italy), Luciano Rizzato from Terzo di Aquileia (Italy), Lorenzo Pomini from Mattarello (Italy), Marco Fin from Bolzano (Italy), Luca Pennacchietti (for the photos) from Falconara (Italy), Luciano Bignami – President of Navimodel Milan (Naviga Italy), the Chiaravalle Modellers Association and, the last but not the least, Norbert and Nadja Thiel, from NNT Modell of Bad Sackingen (Germany).
But, most of all, to my wife Claudia, for her great enthusiasm and support and, certainly, for her enormous patience and sympathy.

Photoetching and resin parts used on the 1:700 Mikuma

Company	Code	Description
Clipper Models	1106	Mogami class 155 mm gun barrels
	1901	Mushroom vents 1,1 mm
	1902	Mushroom vents 0,8 mm
	1903	Mushroom vents 0,6 mm
Eduard	17505	IJN Figures
Fine Molds	AM – 04	IJN Ship’s accessories anchor & chain set
	AM – 08	IJN Vessels type 96 25 mm twin MG
	AM – 11	IJN Vessels radial boat davits set (large)
	AM – 12	IJN Vessels boat accessory set
	AM – 20	IJN Searchlight set 2 for BB – CV – CA
	AM – 24	IJN Catapult Kure type 2 model 3
Flyhawk Model	FH 700002	Arm rest and defend rain along
	FH 700004	Defend the skateboard 1
	FH 700014	Perforate board
	FH 700015	IJN Accommodation ladder
	FH 700016	IJN Swinging boom
	FH 700018	Deck canopy
	FH 700019	IJN Railing
	FH 700022	IJN Binoculars & fire controller
Gold Medal Models	700-4	Yamato set
	700-1	1/700 Naval ship
	700/350-1 D	1/700 – 1/350 Flag decals
Hasegawa	72083	Binoculars and rangefinders
	72105	Battleship Ise & Hyuga detail up parts
Lion Roar	LE 700018	WW 2 IJN Catapults 3
	LE 700025	WW 2 IJN Ship railing 3
	LE 700026	WW 2 IJN Extra ladders
	LE 700027	WW 2 IJN Vessels radial boat
	LE 700033	WW 2 IJN Aircraft deck rail & turntable
	LE 700034	Perforate bar
	LE 700038	WW 2 IJN Ship’s accessory anchor & chain set
	LE 700042	WW 2 IJN 25 mm AA gun set 2
	LE 700044	WW 2 IJN Triangular perforate board
	LE 700049	WW 2 IJN Thermal baffle for IJN type 3 203 mm/50 cal duplex
	LE 700052	WW 2 IJN Watertight door
	LE 700053	WW 2 IJN Cable reel
	LE 700054	WW 2 IJN Hanging ladders
	LE 700067	WW 2 IJN Armored rails & caisson
	LE 700076	WW 2 IJN Naval vessels nameplate
	LE 700089	WW 2 IJN 127 mm AA gun
Pit-Road	PE 123	IJN Heavy cruiser Mogami
	PE 134	IJN Heavy cruiser Mikuma/Suzuya
Tom’s Modelworks	726	WW 2 IJN Heavy cruiser
	727	WW 2 IJN Light cruiser
	742	US Carrier catwalks
White Ensign Models	WEM PE 728	IJN AA weapons
	WEM PE 729	IJN Doors
	WEM PE 736	1/700 – 1/350 Ships wheels

Bibliography

Tamiya News Supplement - Random Japanese Warship details Vol. 1
Tamiya News Supplement - Random Japanese Warship details Vol. 2
Japanese Naval Warship Photo Album - Cruisers
Model Art - Ship Modeling Special n. 8
Navy Yard - Vol. 6 Autumn 2007
Warships of the Imperial Japanese Navy n. 12 - Mogami, Mikuma, Kumano, Suzuya, Tone, Chikuma
Gakken n. 38 - Mogami Class
Mechanism of Japanese Warships n. 3 - Heavy Cruisers
Warships of the Imperial Japanese Navy 1869 - 1945
Drawings of the Imperial Japanese Naval Vessels n. 2
Ships of the World n. 441 - Japanese Cruisers
Gli Incrociatori della Seconda Guerra Mondiale - di Giorgio Giorgerini
Cruisers of World War Two - An International Encyclopedia – M.J.Whitley
Japanese Cruisers of the Pacific War - Lacroix, Wells
All about Japanese Naval Shipboard Weapons

Internet websites:

www.steelnavy.com
www.modelwarships.com
www.combinedfleet.com