Sŏnsan-class destroyer

File:DD Sonsan 1934.png The Sŏnsan as she appeared on the eve of war with Sylva, prior to the addition of other AA weaponry.
Class overview
Name:	Sŏnsan-class destroyer
Operators:	Greater Menghean Empire
Preceded by:	Paengsŏng-class destroyer
Succeeded by:	Sangdong-class destroyer
Built:	1932-1936
In service:	1934-1945
Planned:	11
Completed:	11
Lost:	8
Retired:	3
General characteristics Sŏnsan, 1934
Type:	Destroyer
Displacement:	1,485 tonnes standard (claimed)
Length:	109.1 m at waterline 111.6 m overall
Beam:	10.4 m
Draught:	4.27 m (full load)
Propulsion:	2 steam turbines, 42,000 shp total 2 three-drum boilers 2 shafts
Speed:	36 knots
Range:	3,500 nm (6,480 km) at 15 knots
Complement:	218
Armament:	2 × 2 130mm L/55 Type 32 naval gun 6 × 12.5mm machine gun 2 × 3 550mm trainable torpedo tube depth charges

The Sŏnsan-class (Menghean: 선산급 구축함 / 善山級驅逐艦, Sŏnsan-gŭb Guchugham) were a series of eleven destroyers built for the Imperial Menghean Navy during the late interwar period, with the last five ships commissioned into service after war with Sylva had already begun. The first Menghean destroyers to incorporate twin-gun turrets, they set the trend for subsequent destroyer construction in the Greater Menghean Empire.

Background

The signing of the 1930 amendment to the Septentrion Nine-Power Naval Treaty imposed new limitations on the construction of destroyers, including a requirement that no more than 16% of each signatory's destroyer tonnage could take the form of vessels displacing more than 1,500 tonnes each. Faced with this limit, the Imperial Menghean Navy set out to design the most effective 1,500-ton destroyer possible, in order to make the most of a tonnage cap lower than that of its rivals. To maximize deck space, they mounted the four main guns in two twin mounts rather than four single ones, and lowered the superstructure slightly. The engines were also substantially improved to allow a higher top speed. The result was a compact but well-armed design, similar in some respects to the Hatsuharu-class destroyers produced in neighboring Dayashina.

As with the preceding Daejŏng and Paengsŏng classes, the Imperial Menghean Navy put an emphasis on surface-to-surface combat, with AAW and ASW taking secondary roles. The ships were built without sonar, and would presumably fire their depth charges with the help of manual spotting or direction from other ships. They also carried a very light secondary AA armament, though in this respect they were not unlike contemporary destroyer classes in other countries. The ships' primary role, in the view of the interwar IMN leadership, was to drive off enemy destroyers and light cruisers with their powerful main guns, while also engaging heavier ships with the improved-range Type 23-II torpedo.

Design

In comparison to the preceding Daejŏng class, the Sŏnsan-class destroyers pioneered a new configuration which would be carried forward to future Menghean light combatants. To conserve deck space, the four main guns were mounted in two twin turrets, one forward and one aft. The bridge was relatively low and compact in comparison to post-WSS Menghean destroyer designs, with two enclosed levels above the main deck and a semi-protected spotting deck on the roof. This included a centralized fire-control tower for the guns, which had a substantial blind spot to the rear because of the placement of the foremast and funnel.

Behind the bridge was a small tripod mast, another feature carried forward to later destroyer classes, with a small enclosed platform for spotting on top. The funnels, aft of here, alternated with the torpedo tubes, another space-saving arrangement over the Daejŏng-class were both torpedo tube sets were aft of the #2 funnel. Behind these was a long deckhouse, topped by a second mast, a searchlight, and a twin machine-gun turret, and finally the second gun turret followed by depth charge racks on the quarterdeck. Owing to structural constraints, a lot of the freed-up space went unused at first, but in subsequent refits the aft deckhouse and the areas port and starboard of the funnels would be used to support additional light- and medium-caliber AA guns.

Gun armament

The main armament of the Sŏnsan class consisted of four powerful 130mm L/55 Type 32 naval guns, the same armament carried by the preceding Daejŏngs. The twin turrets that carried them, however, had powered traverse and elevation controls, allowing them to track moving targets more effectively and better respond to the ship's own maneuvers. They also had floors and shell ready racks which traversed along with the gun shield, features not present on preceding Menghean destroyer classes, allowing a modest improvement in rate of fire. Though not fully enclosed - the rear of each turret was left open, and could only be covered with a roll of canvas hanging above - the "R type" dual turret was a major improvement and would appear on Menghe's next three destroyer classes and a few lighter ships.

Shells were hoisted into the "turrets" along lightly armored pulleys which extended through the hull of the ship into the magazine. These pulleys were capable of lifting six complete rounds of ammunition per minute, according to Navy documents, though turret crews could temporarily exceed this rate of fire by using shells from ready racks in the turrets themselves. This system was an improvement over the Daejŏng class, where rounds were hoisted to the deck separately and manually passed or carried to the turrets, a difficult process in heavy seas.

The designers originally intended for the powered twin mounts to have a secondary anti-aircraft capability, something other major naval powers were experimenting with during the same time period. The long recoil stroke of the 130mm L/55 guns left little space for high elevation, however, and the final "R-type" mounting only permitted a maximum elevation of 45 degrees. While this was largely inadequate for defense against aircraft other than torpedo bombers, it did extend the anti-surface range to 25.7 kilometers, allowing the destroyers to engage other vessels from a greater distance.

Anti-aircraft armament

Apart from her minimally effective dual-purpose mounts, the Sŏnsan was built with six 12.5mm water-cooled machine guns spread across five mounts, one of which was a twin mount that could fire to either side or directly astern. Weapons of this caliber were considered adequate for naval anti-aircraft combat at the time of the ships' construction, but combat experience against Sylvan aircraft in 1935 and 1936 revealed that their 1-kilometer effective range was at best mediocre.

The last three ships in the class, Jochŏn, Yugu, and Baeksa, were completed with two 40mm Type 21 anti-aircraft guns salvaged from early-interwar storage. These were placed in a superfiring arrangement atop the deckhouse just forward of the Y turret. These ships also received additional 12.7mm machine guns on either side of the #2 funnel, and dual mounts on either side of the bridge.

Even so, it was not until the arrival of the 37.5mm Type 38 anti-aircraft gun that the Imperial Menghean Navy gained an effective air defense weapon. These guns were mounted on the Sŏnsans during 1939 and 1940, as deliveries to larger warships had received greater priority. Further increases in anti-aircraft firepower would take place over the course of the war, with individual hulls differing slightly in their combination and arrangement of autocannons.

Torpedoes

The Sŏnsan-class destroyers were built with two triple launchers for 550mm torpedoes, both in centerline mounts. These were designed to be compatible with the new Type 23-II torpedo, introduced in 1933, which could travel further than the standard Type 23-I: 4,000 meters at 45 knots, 8,000 meters at 35 knots, and 11,000 meters at 31 knots. While not as long a range as the Dayashinese Type 93 torpedo, this was nevertheless an impressive range for a wet-heater torpedo entering service in 1933, and it allowed the Sŏnsans to engage enemy capital ships from safer distances.

During early-war refits, the Sŏnsans were given accommodation for six additional torpedo reloads, which were stored in lightly protected boxes mounted on the deck. Reloading of the torpedo tubes was an entirely manual process, and could take in excess of 30 minutes even on steady seas outside of combat. Above-deck torpedoes were also exposed to enemy fire, and their 5-millimeter-thick boxes were at best marginal at stopping shrapnel from nearby shell hits and machine-gun fire from strafing aircraft.

Propulsion

Propulsion came from two oil-burning water-tube boilers, each located underneath an equally-sized funnel. The boilers were of a newer type than those on the Daejŏng class, but they still used saturated steam and were not considered state-of-the-art. Steam from the boilers drove two geared turbine sets just abaft them, for a maximum output of 42,000 shaft horsepower. At this level, the destroyers could reach a top speed of 36 knots. The more minimal superstructure and lack of superfiring guns resulted in a lower center of gravity than previous Menghean destroyer classes, giving the Sŏnsans fairly good stability in rough seas, and the class did not suffer the same structural problems as contemporary Dayashinese destroyers of similar size but (initially) greater armament.

Cruising range, at 3,500 nautical miles (6,480 kilometers), was better than that of the Daejŏng-class, though still not excellent. It was sufficient to allow greater autonomy when on patrols of the South Menghe Sea and the Innominadan coast, but not enough to support prolonged convoy-raiding operations in the Helian Ocean, a task ultimately left to later destroyer classes.

Operational history

When Menghe declared war on Sylva in 1935, six Sŏnsan-class destroyers had already been commissioned out of a total production run of 11 hulls. These ships supported the initial offensive to take Altagracia, patrolling the peninsula's waters just outside the range of coastal guns to intercept any vessels attempting to enter or leave. On the night of May 8th-9th, the destroyer Myŏnwŏn fired on the ocean liner Santa Maria on the suspicion that Sylvan colonial officials were attempting to flee aboard, killing several dozen civilians after the ship caught on fire and the passengers abandoned ship.

Sŏnsan-class destroyers also took part in the Battle of Dietmar's Point, where Menghe inflicted a decisive defeat on the Maverican navy, and the Battle of the Portcullia Strait, where they crippled Tyran's naval forces in the Eastern Hemisphere. As these were surface actions, the destroyers' heavy gun and torpedo armament served them well. They were less prepared to confront other threats, and by 1938 two had been lost - Daejŏ to Sylvan coastal bombers flying out of Innominada, and Hwasun to Tyrannian dive bombers flying out of Portcullia. While deadly against torpedo bombers, the "R-type" turrets lacked the elevation to engage high-flying aircraft, a flaw which Allied pilots learned to exploit.

Between 1938 and 1940, all surviving ships in the class were fitted with 37.5mm anti-air guns to address this vulnerability, though they did not receive new turrets. They were also fitted with sonar and hydrophones, as part of a wider IMN effort to convert obsolete light surface combatants into ASW vessels. Low-grade electronics in the submarine-detection equipment and outdated submarine-hunting tactics hamstrung their efforts, however, and by the war's end four Sŏnsan-class destroyers were lost to submarines. Allied aircraft also took a heavy toll on the Sŏnsans when they were pressed into service as carrier escorts.

Only three destroyers in the class survived to the end of the war: Sŏnsan, Muryong, and Yugu. Of these, the Sŏnsan and Yugu were sold for scrap, though the latter was lost while being towed to a Dayashinese shipyard and sank in the East Menghe Sea after drifting north. The site of her wreck was found in 2015. Muryong was requisitioned for nuclear tests against a simulated enemy fleet, and sank in 1946 after sustaining damage from an atmospheric nuclear blast.

Ships in class

Documents from 1931 suggest that the Navy initially intended to order 16 Sŏnsan-class destroyers, the same number as the Daejŏng-class and a good match for the IMN's practice of organizing destroyer squadrons out of four ships each. Instead, eleven Sŏnsans were laid down and completed in all, with production switching to the similar but improved Imsil-class destroyer in 1934. The 11th Destroyer Squadron was thus comprised of three Sŏnsans rather than the usual four. In keeping with Navy nomenclature of the period, all ships were named after Menghean counties.

Name	Mengja	Laid down	Commissioned	Fate
Sŏnsan	善山	1932	1934	Decommissioned in 1945; broken up in 1948.
Hwasun	和順	1932	1934	Sunk by Tyrannian dive bombers near Portcullia on 9 August 1938.
Myŏnwŏn	綿遠	1932	1934	Torpedoed by OSS Albacore on 21 September 1944.
Sŏnghwan	成歡	1933	1935	Sunk by Columbian dive bombers in 1945.
Daejŏ	大宁	1933	1935	Sunk by Sylvan coastal bombers on 5 July 1936.
Muryong	木岭	1933	1935	Decommissioned in 1945; sunk as a nuclear bomb target in 1946.
Munsang	汶上	1933	1935	Struck by Maverican coastal artillery near Swartzburg on 28 October 1940; abandoned after her crew was unable to control flooding to the machinery spaces.
Ochŏn	烏川	1933	1935	Torpedoed by OSS Seabass on 2 March 1945.
Jochŏn	朝天	1933	1936	Torpedoed by HMS Upholder on 16 April 1944.
Baeksa	白沙	1934	1936	Torpedoed by OSS Grouper on 4 December 1942.
Yugu	維鳩	1934	1936	Decommissioned in 1945; lost in a typhoon while being towed to Dayashina for scrapping in 1947.

See also

• Jinan-class cruiser
• Songrimsŏng-class battleship