Sangdong-class destroyer

File:DD Sangdong 1935.png The Sangdong as she appeared shortly before the outbreak of war with Sylva. Note the recently fitted 75mm guns.
Class overview
Name:	Sangdong-class destroyer
Operators:	Greater Menghean Empire
Preceded by:	Sŏnsan-class destroyer
Succeeded by:	Imsil-class destroyer
Built:	1932-1937
In service:	1934-1945
Planned:	8
Completed:	8
Lost:	8
General characteristics Sangdong, 1935
Type:	Destroyer
Displacement:	2,240 tons standard 2,680 tons full load
Length:	112.7 m at waterline 115.5 m overall
Beam:	10.2 m
Draught:	3.35 m (normal)
Propulsion:	2 steam turbines, 72,000 shp total 4 three-drum boilers 2 shafts
Speed:	38 knots
Range:	6,300 nm (11,670 km) at 15 knots
Complement:	252
Armament:	3 × 2 130mm L/55 Type 32 naval gun 3 × 1 75mm L/55 Type 34 AA gun 6 × 1 12.5mm machine gun 2 × 3 550mm trainable torpedo tube depth charges

The Sangdong-class destroyers (Menghean: 상동급 구축함 / 上東級驅逐艦, Sangdong-gŭb Guchugham), known to the Allies as the Shang Tong class, were a group of eight 2,000-ton destroyers built in the Greater Menghean Empire during the mid-to-late 1930s. Boasting a formidable gun and torpedo armament as well as a high top speed, they were Menghe's most advanced destroyer class at the outbreak of the Pan-Septentrion War. Nevertheless, they suffered a number of structural problems as a result of their lightweight construction, and were some 240 tonnes overweight at the time of commissioning. Modifications to the last three ships corrected some of these problems.

Background

Under the 1930 "cruiser amendment" to the Septentrion Nine-Power Naval Treaty, destroyers were divided into two types: those displacing 600 to 1500 tonnes, and those displacing 1500 to 2000 tonnes. The latter group could only account for 15% of total tonnage in each signatory's destroyer category, a restriction intended to slow the Casaterran arms race toward ever-larger destroyer leaders.

Initially, Menghe had only two ships in the upper destroyer category: the destroyer leaders Paengsŏng and Gŏchang, both under construction at the time the amendment was signed. These vessels resembled enlarged versions of the Daejŏng-class destroyer, with a fifth 130mm gun turret and small-scale command facilities on board. This reflected the IMN's late-1920s doctrine of building dedicated flotilla leaders for its destroyer squadrons. In 1931, however, a political shake-up in the Navy upper leadership passed control to a new set of officers, who believed that Menghe needed large, fast destroyers based on the Sieuxerrian contre-torpilleurs. These ships would have greater speed and armament than other destroyer classes, and would operate independently as their own squadrons, chasing off enemy light combatants and raiding convoys.

These changes demanded a new design with greater range and speed and a better gun arrangement. The Navy's engineering team promptly set to work, modifying "maximum" designs which they had drawn up when the treaty was signed. A winner was announced in 1932, and the first destroyer in the series was laid down near the end of that year. The new ships were constructed simultaneously with the Sŏnsan and Imsil destroyer classes, and were ostensibly intended to operate as their squadron leaders.

Design

Gun armament

The Sangdong-class destroyer was armed with the same "R-type" twin 130mm turret used on the Sŏnsan and Imsil-class destroyers, but with three twin mounts in all, a 50% increase in firepower. Moreover, the turrets were arranged in a superfiring AB+X layout, allowing the Sangdongs to direct four guns - equivalent to a full broadside from a Sŏsan or Imsil - at a target directly ahead. As most contemporary destroyers had only one or two guns facing directly astern, this gave the Sangdong-class an advantage in pursuit missions. The 130mm L/55 Type 32 naval gun used in these mounts also had very good range, accuracy, and penetration, and a decent rate of fire of 10 rounds per minute per gun under ideal conditions.

In theory, the 130mm guns could also be used against aerial targets, but the turrets' 45-degree maximum elevation limited its usefulness. Instead, the Sangdong class relied primarily on its impressive array of medium-caliber AA guns. As designed, each ship carried three 75mm L/55 anti-air guns in shielded mounts, a rather large secondary battery which reflected the designers' anticipation that pursuing ships could come under attack from enemy aircraft. Due to delays in development, the new 75mm guns were not ready for installation until 1935 and the Chŏngsŏng and Hwayang had to use QF 2-prd guns imported from Tyran in the early 1920s due to excessive demand for 75mm AA weapons. These guns had the added advantage of being able to depress to a horizontal angle and engage surface targets.

During later upgrades, the Sangdong-class received increasingly large numbers of Type 38 anti-aircraft autocannons and Type 42 20mm guns, further improving their anti-aircraft firepower. The Navy considered a plan to refit them with "S-type" twin 130mm turrets, which would have given them true dual-purpose AA capabilities, but eventually turned down this scheme due to a shortage of materials.

Torpedoes

While the Sangdong-class was 700 tons heavier than the Daejŏng and Sŏnsan-class destroyers, it was designed with the same torpedo armament: two triple 550mm centerline tubes firing the Type 23 or Type 23-II torpedo. The Navy's design team still considered it primarily an anti-destroyer and anti-torpedo-boat vessel, and noted in some early documents that its high profile and smaller production run made it less than ideal for engaging capital ships.

After Dayashina agreed in 1935 to sell a production license for its Type 93 torpedo, which Menghe produced as the Type 35, the Imperial Menghean Navy decided to mount the new weapon on the Sangdong-class, as its high speed made it an ideal ship for skirmishing against larger but slower formations. The torpedo's long range also allowed the Sangdong to engage with greater safety, possibly without even being spotted. The last three ships in the class were completed in this configuration, and the 610mm triple launchers were retrofitted to the first five in 1939-1940.

Powerplant

The size and displacement of the Sangdong class belied its speed and maneuverability. Power came from two geared steam turbines, each capable of developing 36,000 shaft horsepower. These were driven by four water-tube boilers, two under each large funnel. With a top speed of 38 knots, the Sangdongs were not the fastest destroyers of their time, but they were faster than any Tyrannian or Sylvan destroyer in service. This not only allowed them to chase down most foreign destroyer classes while facing four guns toward the target, it also allowed them to turn about and retreat if they encountered a stronger enemy force.

More significantly at the operational level, the Sangdong class had enough fuel on board to travel 6,300 nautical miles at 15 knots. This was two to three times the range of previous Menghean destroyer classes. At the beginning of the war this was a small advantage, as most naval combat took place off the coast of Innominada and the Sylvan Flota Oriental remained in Maracaibo, but from 1938 onward it allowed the Sangdong class to take part in convoy raiding operations in the Helian Ocean. Even during shorter-range patrols, deeper fuel stores meant the Sangdongs could cruise at 30 knots for extended periods of time.

Anti-submarine warfare

Unlike most previous Menghean destroyers, which omitted submarine-hunting equipment to save weight and space, the Sangdong-class destroyers were designed with sonar and hydrophones from early in the development process. This was partly a reaction to the larger displacement limit, and partly based on the reasoning that if the Sangdong-class operated independently while pursuing destroyers or raiding convoys it might be lured into a trap laid by an enemy submarine. The ships' high speed also meant that when working as convoy or battlegroup escorts they could rapidly move to respond to submarine contacts.

Anti-submarine armament consisted of two depth charge racks and two broadside depth charge launchers, with a total of 24 depth charges stored; this number would increase to 48 later in the war as the IMN became more aware of the threat submarines posed. Hadang and Ryuchan were fitted with a twin-barrel 200mm anti-submarine mortar in 1944 in place of the "B" turret, as an experimental effort to deploy forward-firing ASW weapons, but this was not as effective as the Allies' Hedgehog, Squid, and Mousetrap systems.

Ships in the class

Under its 1931 shipbuilding program, the Imperial Menghean Navy planned to build six 2,000-ton destroyers at a rate of two per year. Combined with the completion of the two Paengsŏng-class destroyer leaders, this would make full use of Menghe's allowed tonnage in the "large destroyer" category. After Rajaama, Ostland, and Dayashina withdrew from the Nine-Power Naval Treaty in 1935, Menghe, already at war with Sylva, promptly followed suit. As a new large destroyer would require additional time to design, the Navy laid down two additional Sangdong-class DDs in 1935 and 1936, bringing the total to eight.

Like all Menghean destroyers of the period, the Sangdongs were named for Menghean counties. All eight ships were lost in combat before the end of the war.

Name	Mengja	Laid down	Commissioned	Fate
Sangdong	上東	1932	1934	Sunk by Columbian dive bombers in 1941.
Sangha	商河	1933	1935	Heavily damaged in a storm in 1936, but repaired; sunk in a Tyrannian surface action in 1940.
Chŏngsŏng	青城	1933	1935	Sunk in a Tyrannian surface action in 1940.
Hwayang	華陽	1934	1936	Torpedoed by a Tyrannian submarine in 1939.
Ryuchan	柳贊	1934	1936	Converted to an ASW ship in 1944. Torpedoed by a Sylvan submarine in 1945.
Jiksan	稷山	1935	1937	Sunk by Columbian dive bombers in 1941.
Dongtae	東台	1935	1937	Sunk by Tyrannian carrier aircraft in 1943.
Hadang	下塘	1936	1938	Converted to an ASW ship in 1944. Sunk by Allied carrier aircraft in 1945.

See also

• Battle of the Portcullia Strait
• Namtong Type 37 bomber