Jinan-class cruiser

File:CL Jinan 1936.png Jinan during patrol duties off Innominada. Note emergency AA gun mounts aft.
Class overview
Name:	Taean-class cruiser
Operators:	Greater Menghean Empire
Preceded by:	Taean-class cruiser
Succeeded by:	Sunchang-class cruiser
Built:	1931-1936
In service:	1935-1944
Planned:	2
Completed:	2
Lost:	2
General characteristics Jinan, 1936
Type:	Light cruiser
Displacement:	8,710 tonnes standard 10,060 tonnes full load
Length:	195.7 m at waterline 199.7 m overall
Beam:	16.8 m
Draught:	7.16 m (normal) 7.45 m (full load)
Propulsion:	2 steam turbines, 86,000 shp total 8 three-drum boilers 2 shafts
Speed:	33.7 knots
Range:	5,500 nm (10,200 km) at 15 knots
Complement:	662
Armament:	3 × 2 200mm L/50 Type 29 naval gun 4 × 2 100mm L/45 Type 28 AA gun 4 × 1 40mm Type 21 anti-aircraft gun 14 × 12.5mm mg (6×2, 2×1) 2 × 4 610mm trainable torpedo tube
Aircraft carried:	1 × Namtong Type 36 floatplane
Aviation facilities:	1 × catapult, recovery crane

The Jinan-class (Menghean: 진안급 순양함 / 鎭安級巡洋艦, Jinan-gŭb Sunyangham were a pair of cruisers built for the Imperial Menghean Navy during the early 1930s. They were a subclass of the Taean-class cruiser, laid down as part of a four-ship order but substantially modified during construction to correct problems which had appeared during the Taean's pre-commissioning trials and early service. As such, they are sometimes considered a separate class of ship, sharing the same hull and main armament but with substantial differences in combat capability. The two ships in the class were known to the Allies as the Chin Ahn and the In Che.

Development

In 1928, the Imperial Menghean Navy ordered four heavy cruisers of the Taean class, which were laid down in 1928, 1929, 1931, and 1932. Following the 1930 amendment to the Septentrion Nine-Power Naval Limitation Treaty, Menghe was limited to 96,000 tonnes in cruisers carrying guns of over 6 inches in caliber, so the Taeans were completed as light cruisers with triple 150mm gun turrets. To bypass the treaty limitations, Menghe built fifteen twin 200mm turrets anyway, in anticipation that if a major war broke out or the treaty fell apart, they could refit the Taeans as heavy cruisers again.

The first ship in the class, Taean, was completed in 1932, but pre- and post-commissioning trials revealed serious problems with her design. In particular, the decision to shave weight off of the hull and thus minimize displacement had created a number of structural problems, which the Navy anticipated would only intensify after the installation of turrets producing a heavier recoil force. The Taean was also found to be underpowered, with a top speed of slightly over 31.5 knots.

In an effort to address these problems, the Navy modified the design of the two hulls still under construction, ordering that they be completed according to a new set of specifications. The hull's internal structure was reinforced, in part through the re-introduction of riveting on areas which had been welded, with particular attention to the bracing structure around the barbettes. The final two hulls also received a brand-new powerplant, consisting of state-of-the-art boilers and turbines built with the guidance of Dayashinese and Ostlandian military advisors. Later in construction, the superstructure of both ships was also modified, to include more high-caliber AA guns and a revised arrangement of the torpedo tubes. While the basic hull form remained the same across the four vessels ordered in 1928, the Jinan and Inje ended up differing substantially in their above-water appearance and capabilites, and as such they are considered at minimum a subclass and possibly a separate class entirely.

Design

Given the similarity between the Taeans and their subclass, Allied recognition guides instructed sailors and pilots to distinguish the two types based on the following three major external characteristics:

• Jinan and Inje have two large funnels of roughly equal size, while the Taean and Kangjin have three funnels, the forward two of which are trunked together into a single large funnel.
• Jinan and Inje have their seaplane recovery equipment in the following order, bow-to-stern: funnel, mast and crane, catapult, turret. On the Taean and Kangjin, the order is: funnel, repair deck, catapult, mast and crane, turret.
• Jinan and Inje have a separate fire-control tower forward of the tripod mast, supporting a large co-incidence rangefinder. On the Taean and Kangjin, the tripod mast rises directly from the top of the bridge.

For a span of two years, the Jinans also carried twin 200mm gun turrets, while the Taeans did not; this changed in 1937 when Taean and Kangjin had their reserve turrets installed.

There were also a number of more subtle external differences between the two subclasses. The Jinans had only two torpedo mounts, both quadruple type and both firing the Dayashinese Type 93 torpedo. They also had a revised arrangement of dinghies and launches, with three small boats on either side of the aft deck. This gave the flak guns a somewhat better field of fire forward, especially when combined with dedicated fire-control and direction towers for anti-air and anti-surface fire.

Armament

Like the other two ships in the original four-hull series, the Jinans were intended to be armed with 150mm triple gun turrets in peacetime and refitted with 200mm twin gun turrets in peacetime, allowing them to circumvent the Septentrion Nine-Power Naval Treaty's tonnage limits by passing as light cruisers. Neither ship, however, was actually commissioned in this configuration: Ostland, Rajamaa, and Dayashina withdrew from the naval treaty in rapid succession in 1935, while the Jinan was still being fitted out prior to commissioning. Seeing that the treaty was about to collapse, Menghe withdrew as well, and the Navy promptly refitted the Jinan with three twin 200mm turrets which had been built already but kept in storage. Inje was completed in this configuration the following year.

The two subclasses differed more significantly in their secondary armament. The Jinans were built with eight 100mm L/40 AAA guns in four turrets, which had power-assisted traverse and elevation controls and protective shields. This change, in combination with improved fire-control equipment, gave them substantially better long-range anti-aircraft protection than their cousin ships. When the Taeans underwent major refits in 1937, one of the first changes the Navy applied was to give them the same model of anti-aircraft turret used on the Jinans, and in time the twin 100mm would become the main heavy-caliber AA weapon on Menghean warships.

In the realm of small-caliber AA, the Jinans were initially to be armed with eight 12.5mm water-cooled machine guns in four single mounts. Combat experience early in the Pan-Septentrion War soon revealed that interwar wargaming had seriously overestimated the effectiveness of shipborne AA, however, and by the time Jinan entered service, the IMN was rushing to improve warships' anti-aricraft protection. One notable change applied to both vessels on completion was the installation of four 40mm Type 21 anti-aircraft guns in single mounts just forward of the seaplane handling mast; these guns had been purchased from New Tyran in the 1920s and mothballed in the 1930s, only to see emergency service again early in the war. By 1939, these would be replaced with the newer 37.5mm Type 38 anti-aircraft gun, which both ships carried in varying configurations.

Following the outbreak of the Pan-Septentrion War, Dayashina agreed to sell Menghe a production license for the Type 93 torpedo, which in Menghe was known as the Type 35. Eight such torpedoes were carried in two quadruple mounts located on either side of the seaplane catapult. While this was fewer than the twelve 55cm Type 23 torpedoes carried by the Taeans, it gave the Jinans the ability to engage enemy capital ship formations from much longer ranges. A semi-automatic reloading system for torpedoes was initially planned but never implemented, due to the limited deck space aft of the mounts.

Protection

Armor protection on the two subclasses was identical, in part because the last two hulls' armor belts had already been installed when the Navy decided to modify the design. This gave her a main belt 75mm thick, an angled armor deck 35mm thick, and a rear transverse bulkhead 125mm thick. The turret faces were 100mm thick, and the barbettes 75mm thick. In all, both subclasses were fairly well protected against cruiser-caliber guns; at regular combat ranges (7,000 to 19,000 meters) they were mostly immune to interwar 6-inch shells, though as guns and ammunition improved, this advantage declined. The IMN concluded somewhat optimistically that they could withstand 8-inch gunfire at a distance of 16,000 to 18,000 meters while facing away from the enemy, and at the Battle of the Portcullia Strait the Kangjin did withstand two 8-inch shell hits to her aft bulkhead. Dedicated heavy cruisers, however, still surpassed them in belt and deck protection, and by the middle of the war the IMN considered them vulnerable as surface combatants.

The Jinan and Inje also shared their cousin ships' poor underwater protection. While their hulls were subdivided into 17 watertight compartments, neither ship had any real layered protection around the boiler and machinery rooms, meaning that a torpedo hit here could paralyze and sink them in short order. After the Kangjin was lost to an aerial torpedo in October 1940, the IMN belatedly responded by fitting the Jinans with anti-torpedo bulges, which modestly improved protection against light torpedoes but reduced their top speed by about one and a half knots.

Propulsion

The largest difference between the Taean and Jinan subclasses in the four-cruiser series was the configuration of their internal machinery. The Taeans carried twelve old and inefficient boilers, which contributed to their disappointing performance: a cruising range of 5,000 nautical miles and a top speed of 31.6 knots. The Jinan and Inje, by contrast, carried eight larger boilers of a newer and more efficient design, capable of handling higher pressures and transferring heat more efficiently. Combined with modified steam turbines, this increased their peak output to --,000 shaft horsepower. Improvements to armament and structural bracing also increased displacement and thus flow resistance, but at full steam the second two cruisers could still reach a top speed of 33 knots. While not outstanding, this put them more in line with contemporary light cruiser designs.

Service

Named for Jinan county in East Chŏllo province, the third cruiser in the broader Taean family was laid down in 1931 and commissioned in 1936. While under construction, she was fitted with triple 150mm gun turrets, but shortly before commissioning these were switched out for twin 200mm gun turrets taken from storage, along with the necessary supporting changes to her ammunition handling and fire control equipment. As such, the Jinan did not take part in the initial fighting at Altagracia, but arrived in time to support the Imperial Menghean Navy's campaign to secure naval superiority along the coast of Innominada.

Her sister ship, Inje, entered service the following year and promptly joined the Jinan in patrols of the Innominadan coast. Though mostly restricted to coastal bombardment missions, the two cruisers performed well in combat, and soon demonstrated the value of their 100mm anti-aircraft guns in defense against Sylvan land-based aircraft. When Menghe declared war on Maverica in 1937, both the Taean and Kangjin were undergoing repairs at Dongchŏn, so the Jinan and Inje took their place during initial surface actions against the Maverican fleet. Here, they proved themselves as effective surface combatants, though Inje suffered a hit to her forward boiler room from coastal artillery and had to withdraw early from the campaign.

Jinan then went on to fight in the Battle of the Portcullia Strait as part of the escort formation for the 1st Battleship Division, sailing in the main line of battle but seeing less action than her cousin ships which fought alongside the Chŏngdo and Sunju. Once the main engagement was over, she withdrew with the rest of the fleet to Nueva Meridia for minor repairs, then supported the landings on Portcullia and northern Khalistan.

Both ships in the subclass then went on to see extensive service along the west coast of Khalistan, where they supported the Army's advance along the shore and attempted to interfere in Tyrannian supply shipments from Casaterra. Owing to their good combat characteristics and limited range, the Navy tasked them with patrolling the area west of the Acheron islands in combination with light escorts, to prevent Tyrannian warships there from attacking the Imperial Menghean Navy. Here, they repeatedly clashed with the Royal Navy, and while neither ship suffered particularly heavy damage, they were not successful in defeating enemy cruisers either. Official reviews of their combat performance indicated that a low rate of fire from the cramped turrets, among other things, handicapped their combat performance in relation to larger heavy cruisers.

Following the Battle of Swartzburg, in which all four cruisers in the Taean family took part and the Kangjin was sunk by a torpedo hit, the Navy withdrew both ships in the Jinan class to Haeju, where they were fitted with anti-torpedo bulges to improve their underwater protection. Part of the new void space was used to store additional fuel, extending the ships' range to 8,000 nautical miles, but the increased displacement also cut into their top speed. They returned to service in 1941, complete with additional anti-aircraft guns, but remained obsolete in comparison to more recently completed heavy cruisers. The IMN relegated them to fleet escort duties for aircraft carriers, which it had belatedly come to regard as the lynchpin of naval combat.

Ships in class

Name	Mengja	Laid down	Commissioned	Fate
Jinan	鎭安	1931	1935	Sunk by Columbian dive-bombers in 1941.
Inje	麟蹄	1932	1936	Sunk by Tyrannian dive-bombers in 1944.

See also

• Paengsŏng-class destroyer
• Songrimsŏng-class battleship