Anchŏn-class battleship

Anchŏn class

<imgur w="300px">eD98cmV.png</imgur> Haeju, Anchŏn's sole sister ship, as she appeared upon commissioning.
Class overview
Name:	Anchŏn class
Builders:	Kimhae Naval Yard Gyŏngsan Naval Yard
Operators:	Greater Menghean Empire
Preceded by:	Songrimsŏng-class battleship
Succeeded by:	Chŏngdo-class battleship
Built:	1919–1923
In service:	1922–1945
Planned:	2
Completed:	2
Lost:	2
General characteristics (as built)
Type:	Dreadnought battleship
Displacement:	33,504 long tons standard 36,713 long tons full load
Length:	213.2 m (waterline) 216.3 m (overall)
Beam:	30.2 m
Draft:	9.45 m normal 9.76 m full load
Installed power:	64,000 shp 4 steam turbines 20 water-tube boilers
Propulsion:	4 shafts
Speed:	24.3 knots
Range:	5,000 km at 14 knots
Complement:	1,324
Armament:	4 × twin 40cm/45 Type 19 naval gun 18 × single 15cm/40 Type 11 naval gun 8 × 7.5cm/45 Type 16 AA gun 4 × 533 mm torpedo tubes
Armor:	Waterline belt: 350mm Deck: 150mm over magazines and machinery Gun turrets: 350mm on face Barbettes: 350mm Conning towers: 400mm Torpedo bulkhead: 75mm
General characteristics (1938)
Displacement:	34,899 long tons standard 37,612 long tons full load
Length:	213.2 m (waterline) 216.3 m (overall)
Beam:	30.2 m
Draft:	9.75 m (normal) 10.01 m (full load)
Installed power:	80,000 shp 4 steam turbines 10 water-tube boilers
Propulsion:	4 shafts
Speed:	25.7 knots
Range:	6,000 kilometers at 14 knots
Complement:	1,976
Armament:	4 × twin 40cm/45 Type 19 naval gun 18 × single 15cm/40 Type 11 naval gun 8 × single 10cm/45 Type 27 AA gun 6 × single 37.5mm Type 37 AA gun 12 × twin 12.5mm water-cooled machine gun
Armor:	Turret face: 400mm
Aircraft carried:	2 × floatplane
Aviation facilities:	2 × catapult 1 × recovery crane

The Anchŏn-class battleships (Menghean: 안천급 전함 / 安川級戰艦, Anchŏn-gŭb jŏnham), known to the Western Allies as the Ahn Tsohn class, were a pair of battleships built in the Federative Republic of Menghe during the late 1910s and early 1920s. Among the battleships retained by Menghe under the Septentrion Nine-Power Naval Treaty, they underwent extensive reconstruction in the early 1930s to improve their combat capabilities. The changes included new engines, a rebuilt superstructure, and improved turrets, though the main armament of eight 40cm naval guns remained the same.

At the outbreak of the Pan-Septentrion War in 1935, the Anchŏn and her sister ship Haeju made up the Imperial Menghean Navy's First Battleship Division. They took part in coastal bombardment operations at Altagracia, but did not fire their guns at another warship until 1938, when both ships took part in the Battle of the Portcullia Strait. Anchŏn and Haeju survived the battle, but both sustained heavy damage after drawing fire from most of Task Force Q, and they were under repair until early 1939. The First Battleship Division spent the remainder of the war performing coastal bombardment duties along Khalistan and Maverica. The ships avoided direct contact with the OS Navy, but came under sustained attack from carrier aircraft late in the war; Haeju sank in shallow water near the city of Sunju and was converted to an anti-aircraft platform, while Anchŏn was sunk by a submarine near the city of Wihae, both in 1945.

Background

At the end of the War of the Sylvan Succession, Menghe had two Songrimsŏng-class battleships in operation and a third nearing completion, all of them domestically built by Menghean shipyards. While the Songrimsŏngs were generally comparable with foreign battleships, they seemed at risk of falling behind a new post-war generation of battleships with larger guns and thicker belt and deck armor. Early in 1919, the Federal Menghean Navy sought permission to build three new battleships armed with 40cm guns in three twin turrets, as a heavier supplement for the Songrimsŏng and her sister ships. The two battleship formations were to operate independently or in tandem, and would effectively replace the Chŏlsŏng and Hwaju classes, which were nearing obsolescence.

The Menghean Parliament was reluctant to allocate funds for such a "Three-Three" fleet plan, especially in light of rumors that the Navy was already planning subsequent battleship classes. After hard bargaining, the civilian government approved the construction of two battleships of the new design, albeit with an implicit offer that the Navy could order more advanced warship classes in the near future if the situation demanded it. The first ship of the class was laid down in October of 1919 at the Gyŏngsan Naval Yard, with her sister ship laid down the following year.

Design

In terms of their basic configuration, the Anchŏn and her sister ship were similar to the Dayashinese Nagato-class battleships or the Columbian Colorado-class battleships. Their main armament consisted of eight 40cm guns arranged in four superfiring two-gun turrets, and their full-load displacement came in at a little under 37,000 metric tonnes. Though relatively slow compared to the fast battleships that would follow, they had respectable performance, and fairly strong armor and torpedo protection.

Armament

<imgur thumb="yes" w="500" comment="The battleship Haeju as she appeared after her first round of refits, during the Battle of the Portcullia Strait.">MGC2j44.png</imgur> The main guns on the Anchŏn and Haeju were designated Type 16 40cm L/45. They used an Elswick-style 3-motion short-arm breech, and were reloaded at a fixed elevation of 5 degrees, meaning that the rate of fire was lower at high gun elevations; the "optimal" firing cycle at 5 degrees was reportedly 22 seconds. Elevation on the first-generation turrets ranged from -5 to +30 degrees, with maximum elevation increasing to 42.4 degrees after mid-life refits. Range and penetration values for the Type 33 Armor-Piercing shell used throughout the Pan-Septentrion War are as follows:

Elevation	Range	Striking velocity	Angle of fall	Penetration (side)	Penetration (deck)	Time of Flight
0.5 degrees	850 m	755 m/s	0.5 degrees	742 mm	--	1.3 seconds
5 degrees	9,100 m	582 m/s	6.0 degrees	550 mm	--	13.6 seconds
10 degrees	15,200 m	488 m/s	13.5 degrees	448 mm	48 mm	25.8 seconds
15 degrees	20,400 m	442 m/s	22.4 degrees	402 mm	98 mm	36.2 seconds
20 degrees	24,900 m	426 m/s	30.5 degrees	342 mm	129 mm	45.8 seconds
25 degrees	28,100 m	419 m/s	38.4 degrees	302 mm	151 mm	58.2 seconds
30 degrees	30,800 m	423 m/s	44.5 degrees	261 mm	204 mm	67.9 seconds
42.4 degrees	36,600 m	457 m/s	54.8 degrees	198 mm	271 mm	92.5 seconds
46.5 degrees*	38,000 m	460 m/s	58.2 degrees	176 mm	302 mm	96.7 seconds

*Maximum elevation on coastal batteries using the gun.

Magazines for the main guns carried 110 shells and 440 quarter-charges per gun, or 880 rounds in total. The shell cage for lifting ammunition carried four stacked charges side-by-side with one shell, allowing easy ramming in two motions. The guns were mounted separately, and could be loaded, elevated, and fired independently of one another.

During major refits in 1932 and 1933, the ships were equipped with new main battery turrets which were essentially scaled-down versions of the turrets on the Chŏngdo-class battleships. The larger firing ports and deeper turret floors allowed an increased maximum elevation of 42.4 degrees, extending the theoretical maximum range by 6,000 meters. They also added new protection within the turret, with double-layered bulkheads between the individual gun compartments and between the upper turret and the ammunition handling room below. These were intended to reduce the extent of the damage if the turret suffered a penetrating hit, or if a gun misfired. The turrets' frontal armor was increased to 400mm, and the turret shape was revised to leave the sides less vulnerable to angled fire. Other changes included the installation of larger co-incidence rangefinders in the turret rear and the addition of saluting guns over the main guns.

The secondary armament consisted of eighteen Type 11 15cm L/40 breech-loading guns in casemate mounts, nine per side. These were the same secondary gun type used on the preceding Songrimsŏng-class battleships. They had a maximum range of 18,000 meters in their initial mounts, and a maximum practical rate of fire of about 5 rounds per minute. During mid-life refits, the mounts were replaced with new Type 30 L/50 guns in revised casemates which allowed a higher elevation, increasing the secondary battery's effective range.

Anti-aircraft armament initially consisted of four 7.5cm high-angle guns and eight Vickers machine guns, but over the course of the ships' service lives it was steadily increased to meet the increasing threat from carrier aircraft. Refits in the early 1930s converted the anti-aircraft armament to eight 10cm Type 29 anti-air guns and ten 12.5mm water-cooled machine guns; in 1937, the designers added six single 37.5mm Type 37 anti-aircraft guns and relocated some of the machine-guns, bringing the total to twelve. After the Battle of the Portcullia Strait, the Imperial Menghean Navy used the ships' repair period to install greatly improved flak defenses, with eight twin 10cm guns in mounts with improved traverse and elevation. The number of 37.5mm and 20mm autocannons steadily increased over the course of the ships' lifetimes, especially after the Haeju was converted to a coastal AA defense platform.

The Anchŏn-class battleships were built with underwater 550mm torpedo tubes, each of which came with three torpedo reloads. Two tubes faced each broadside; there were no bow or aft tubes. The torpedo magazines and handling rooms were included within the ship's armored citadel, but they did interrupt the layered structure of the ships' torpedo protection. They were removed during refits.

Protection

Anchŏn was the first Menghean battleship to incorporate "all-or-nothing" armor protection on her hull, with a 350mm main belt running around the magazines, turbines, and boilers but no waterline armor protection forward or aft. The main belt did, however, wrap around the forward and aft ends of the citadel with transverse bulkheads. A 150mm upper belt above the main belt provided additional protection. Deck armor consisted of a 100mm "turtle-back" armored deck over the citadel and a 50mm armored deck one level above it; the spacing was intended to de-cap armor-piercing shells or detonate them prematurely. A 25mm, later 75mm, armored plate over the quarterdeck provided some protection to the rudder and steering equipment. This armor configuration was generous for the time, and it would allow the Anchŏn and Haeju to remain afloat despite suffering numerous direct hits at the Battle of the Portcullia Strait.

Armor on the ship's armament was comparable. The main battery barbettes had armor plating 350mm thick, and the turret faces were 350mm thick, later increased to 400mm. Turret armor was 150mm thick on the sides and 100mm thick on the roof and rear. The secondary battery barbettes were 125 millimeters thick. The best-protected area was the forward conning tower, at 400 millimeters thick.

Unlike the Songrimsŏngs and their predecessors, all of which had relied on torpedo nets for defense in port and would later have to be refitted with anti-torpedo bulges, the Anchŏn-class battleships were built from the keel up with internal torpedo bulkheads to limit torpedo damage. These bulkheads, 50 millimeters thick, ran the full length of the armored citadel, covering the magazines, boilers, and turbines. Outside of the bulkheads were alternating compartments containing air and fuel oil to absorb the pressure wave from a torpedo's detonation. Individual rooms and compartments in the bow and stern could also be sealed with watertight doors to contain flooding.

Propulsion

As built, the Anchŏn and Haeju were powered by four 16,000-horsepower (11,900 kW) steam turbines paired with twenty water-tube boilers. These burned a mixture of coal and oil, with the former used for cruising and the later sprayed onto the fuel when higher output was necessary. As on many other battleships of the time, smoke from the forward funnel frequently blew onto the foremast's observation deck before refits. At full steam with a normal combat load, the ships could reach a top speed of 24.3 knots.

During comprehensive refits in 1932 and 1933, the inefficient and outdated coal-oil boilers were replaced with twelve oil-fired boilers trunked into a single funnel. The turbines were also upgraded, allowing a maximum combined output of 80,000 horsepower across four shafts. Due to the increased mass added during refits, the ships sat lower in the water with this configuration, and top speed only increased to 25.7 knots. Range increased only modestly, to 6,000 nautical miles at 14 knots.

Aircraft

As part of their mid-life refits, each ship was fitted with two aircraft catapults, each carrying a single floatplane. These were located on either side of the ship on the aft deck, forward of the #3 turrets. A single crane aft of the catapults could be used to recover planes once they taxied to one side of the ship. Menghean designers initially favored this type of amidships catapult, as it allowed two aircraft to be carried yet it did not interrupt the firing arcs of the aft turrets. This configuration did, however, reduce the available deck space for anti-aircraft guns.

After the Battle of the Portcullia Strait demonstrated the importance of carrier aircraft in attacks on large surface vessels, the Imperial Menghean Navy altered the ships' design during their repair period, removing the amidships catapults and replacing them with a single catapult arm on the quarterdeck. Two reconnaissance aircraft could be carried: one on the catapult, and one on the quarterdeck adjacent to it.

Ships in class

A total of two Anchŏn-class battleships were produced. In keeping with Menghean nomenclature tradition, they were named after Menghean cities - specifically, the cities of Anchŏn and Haeju, both located along the eastern coast. Collectively, these two warships formed the First Battleship Division, and they generally operated together to facilitate maintenance and logistics.

During the early interwar period, the First Battleship Division patrolled the eastern coast of Menghe, part of a buffer against Dayashina. After war with Sylva broke out in 1935, they took part in the bombardment of Altagracia, and patrolled the southern coast as a deterrent against the Sylvan battleships stationed in Maracaibo. In 1938, the First Battleship Division joined the rest of the Combined Battle Fleet to inflict a decisive defeat on the Tyrannian Royal Navy at the Battle of the Portcullia Strait, though both ships sustained heavy damage and underwent major reconstruction in late 1938 and early 1939.

Anchŏn

<imgur thumb="yes" w="500" comment="The battleship Anchŏn in 1940, after her major repairs and refits. Note the relocated floatplane catapult and the increased anti-aircraft armament.">g90Op5V.png</imgur> Laid down on 3 May 1919 at the Gyŏngsan Naval Yard, the Anchŏn (Menghean: 안천/安川) was commissioned on 19 June 1922. She was the first ship of the class. Under the Stuart-Lavender romanization system in Western use at the time, she was known as Ahn Tsohn.

Haeju

Haeju (해주/海州), known to the Western Allies as Hai Chu, was laid down on 21 June 1920 at the Kimhae Naval Yard and commissioned on 30 September 1923. She was identical in construction to her sister ship. Haeju became famous for firing the shell that detonated the magazine of HMS Indomitable at the Battle of the Portcullia Strait, sinking the latter ship in a matter of minutes. Like her sister ship, Haeju was significantly rebuilt after the battle, though she ultimately mounted a different seaplane assembly.

On the night of June 4-5, 1944, when both battleships were anchored in Sunju Harbor, Columbian carrier aircraft attacked them in port, part of a daring raid along the south Menghean coast. The Haeju sustained multiple torpedo hits and began taking on water. Fearful that the ship would sink, Captain Ha steered her toward the shallow coastal waters near the mouth of the Chŏllo river, where she ran aground in the early hours of the morning. The ship settled on the soft mud deposited by the river, and the entirety of her weather deck remained above the waterline, though her aft freeboard was reduced to less than a meter. The Imperial Menghean Navy determined that it was too costly and too dangerous to mount a salvage operation, and instead the stationary wreck of the Haeju was converted into an anti-aircraft platform through the addition of more medium-caliber AA guns. Her umbrella of AA fire provided some protection for the light vessel docks and repair yards nearby, and she remained operational for several months despite repeated attacks from Allied dive-bombers and strategic bombers. On August 14th, bombs from a dive-bomber raid set off a fire on her fore deck, which gradually spread to the medium-caliber AA magazines; when the fire was extinguished the following day, the high-caliber AA guns were damaged beyond easy repair, and only small- and medium-caliber AA guns could be re-mounted. The wreck was broken up in 1946.

See also

• Songrimsŏng-class battleship