8-inch Coastal Defense Guns
by Dirk H.R. Spennemann
Battery Lay-outs

The 8-inch guns, both naval guns and the short 1943 model naval guns, have been reported in a number of battery lay-outs, but usually in groups of two.

On Betio (Tarawa Atoll, Kiribati) two batteries of two guns each have been reported:

(i) The S.W. battery consisted of two guns emplaced offset but above each other (figure 20). The lower gun had a traversing circle of 270°, while the top gun could be traversed through 360°. Maximum elevation of both guns is estimated to have been 30°.

(ii) The S.E. battery consisted of two concrete emplacements set 100m apart. An ammunition ready room was built at the emplacement on the landward side, restricting the guns’ traverses to 300° (ISSMD/JICPOA 1943).

A similar set up was utilised on Eneen-Kio, where the guns were set up in pairs set some 70m apart, with a rangefinder on a tower set back between the two emplacements.

Gun Emplacements

Short naval guns

High angle, short-barrelled 200mm guns were sited in a variety of emplacements: open emplacements, similar to those used for other calibers, open concrete revetments and casemates and cave positions. The environment governed the choice of emplacement.

Open concrete revetments were usually emplaced at fixed positions with limited firing arcs and consisted of high vertical blast walls (2.7m tall) or a bunker-type enclosure with a large firing port to allow for the high angle fire of the gun. Concrete revetments had ammunition recesses on three side of the guns

The emplacements for the 200mm short naval gun could also be merely small concrete pads set in open log enclosures, or straight on reinforced ground (OPNAV 1945a, p. 59).

Long-barelled naval guns

The gun emplacements of the large naval guns encountered in Betio, Eneen-Kio and Sapuk are of mixed types, but all open. The emplacements on Betio and Eneen-Kio are concrete parapet emplacements with the entire emplacement banked with sand and coral (OPNAV 1945a; ISSMD/JICPOA 1943; Cohen 1983). The revetment walls are of thin concrete (on Eneen-kio), prone to erosion. The emplacement on Chuuk have been revetted with natural stone set in a herring bone fashion (figure 22). Retaining walls, where necessary, have been made in the same fashion.

The emplacements have an inner diameter of 39 to 40 feet (12m), with the ammunition trough being placed 16.5 to 17 feet away from the center of the turret.

All turrets appear to have been placed on a sand-filled steelpate and angle base, with a large servicing room for the traversing gear and electromotor underneath.


Figure 17. Lay-out of an 8-inch battery at Sapuk, Moen Island, Chuuk Atoll, FSM (after Denfeld 1979).


Figure 18. Lay-out of a tandem 8-inch battery at Betio, Tarawa Atoll, Kiribati (after OPNAV 1945).


Figure 19. Lay-out of a tandem 8-inch gun emplacement at Betio, Tarawa Atoll, Kiribati (after OPNAV 1945).


Figure 20. Lay-out of an emplacement of an 8-inch battery at Betio, Tarawa Atoll, Kiribati (after OPNAV 1945). Similar emplacements were used on Eneen-kio.


Figure 21. Sapuk, Moen Is. Chuuk Atoll. Gun emplacements made of locally collected rock set in herringbone fashion. close-up of emplacement of nº 1 gun.


Figure 22. Underground ammunition Magazine for 8-inch guns encountered at Betio, Tarawa Atoll, Kiribati (after Vincent 1943).


Figure 23. Sapuk, Moen Is. Chuuk Atoll. Ammunition locker between guns nº 2 and nº 3. (Photo: Dirk H.R. Spennemann)

Ammunition Supply Buildings

The ammunition (at Betio) was stored in a heavily constructed bomb-proof shelter set approx. 75m from the gun emplacements. The ammunition supply occurred via narrow gauge railway with hand drawn cars from a shielded ammunition depot to an ammunition ready magazine near the guns. The ammunition supply buidings always have two compartments, with separate entrances; one served for the shells, the other for the powder, which was usually stored in metal canisters (for satchel charges) or in semi-fixed Cu-alloy cartridges.

On Betio (S.W. battery) the ammunition ready room was made of 30-inch reinforced concrete wall, and measured 12.5 by 10 feet in size. A single ammunition ready room served for both shells and propellant cartridges or satchel charges.

Fire Control

In the SW battery of Betio the fire control was in a plotting room underneath the upper gun, linked by voice tube to a 70’ tower which held the director and the range finder. In the SE battery a 45’ tower placed between the two emplacements, set back by 30m metres.

Power Stations

Since in the main the gun was trained and pointed electrically, a power suppy was required. A small power station was usually set up some 50-100m away from the emplacements.

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Bibliographic citation for this document

Spennemann, Dirk H.R. (2000). 8-inch Coastal Defense Guns. British, Italian and Japanese Naval Guns and their Emplacements in Micronesia.
URL: http:/marshall.csu.edu.au/Marshalls/html/Sapuk/Sapuk.html

Dirk H.R. Spennemann, Institute of Land, Water and Society, Charles Sturt University, P.O.Box 789, Albury NSW 2640, Australia.
e-mail: dspennemann@csu.edu.au

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