On August 8th 1945, the fourth and last Yamato class battleship, HIJMS Kwanto, was commissioned into the Imperial Japanese Navy. The cheering crowds and assembled dignitaries were doubtless much impressed by the sight of the four great battleships sitting in Kagoshima Bay. There was no doubt that completing the last of the four ships had given Japan a squadron of the largest and most powerful battleships ever built. What only a few professional analysts understood was that the proud show being put on by the Japanese Navy was just that, a show. In reality, the Japanese Navy was a fleet in crisis.
Part of the crisis was with the battleships themselves. The Battle of the Orkneys was still in the future but even before the murderously thorough destruction of the German fleet, naval professionals knew that the future of naval warfare lay with aircraft carriers not battleships. To them, it was clear that, by squandering resources on the four behemoths sitting in the bay, Japan had forgone the opportunity of building both a substantial carrier fleet and replacing its battle line. Of the existing battleships, the six old dreadnaughts of the Fuso, Hyuga and Nagato classes were so obsolete that their retention in service was just a waste of resources. The four Kongo class battlecruisers were scarcely any better; they were fast but that was all. Their armor was paper thin and their gunpower limited. In reality, the four Yamato class battleships were not a powerful addition to the Japanese Navy's battle line, they were the Japanese Navy's battle line.
The aircraft carrier fleet was nominally in good condition. In the 1930s, the Japanese Navy had designed two classes of aircraft carrier as the standard for future production. These were the two Shokaku class ships, Shokaku herself and her sister Zuikaku, and a single Taiho class carrier. The two classes were roughly equal in size but the Shokakus were relatively flimsy and ill-protected, concentrating instead on carrying a large airgroup of up to 84 aircraft. The Taiho was much tougher with flight deck and extensive side armor but paid for that protection with a smaller group, up to 54 aircraft maximum. The two types were designed to work together, the Taihos engaging enemy carriers in a slugging match while the Shokakus stood back and launched decisive strikes. Further building plans had added five more Taihos and four more Shokakus to the fleet. The problem was that those new carriers were coming slowly. Some would take up to eight years to build.
Oddly though, the real crisis lay not in Japan's capital ships but in her destroyer and light cruiser forces. This was ironic because Japanese destroyers had been the yardstick of naval production throughout the 1930s, universally admired for their speed and firepower. As with the battleships, the superficial impression was highly misleading. The truth was that most of Japan's destroyer fleet was obsolete. At least half the available destroyers were pre-"Special Type", officially listed as "second class" and devoid of any effective anti-aircraft or anti-submarine capabilities. The early "special types" were also essentially defenseless against air attack. There was no doubt that the destroyers were very effective vessels for surface combat but that was all they could do. Only the most recent classes had a more balanced capability.
The effective Japanese destroyer fleet consisted of three primary types of destroyer. The most numerous were the 48 "Type A" destroyers of the Yugumo/Kagero classes. There were 390 foot long, 2,500 ton ships armed with six 5 inch L50 dual purpose guns in three twin turrets and 12 25mm anti-aircraft guns in four triple mounts. They had eight 24 inch torpedo tubes with 8 reloads for a total of 16 torpedoes. They were capable of 35 knots and had a range of 5,000 miles at 18 knots.
The second most numerous type of destroyer was the "Type B" specialized anti-aircraft destroyer. There were 12 Akizuki class destroyers, displacing 2,700 tons standard and armed with eight 3.9 inch L65 dual purpose guns in four twin turrets, six 25mm guns in two triple mounts and four 24 inch torpedo tubes with one set of reloads for a total of eight torpedoes. The Type Bs were 440 feet long with a maximum speed of 33 knots. Their operational range was 8,300 miles at 18 knots.
The final group of destroyers were the eight Type C" Shimakaze class. These were 2,600 ton ships, 415 feet long and armed with six 5 inch L50 dual purpose guns in three twin turrets, six 25mm guns in two triple mounts and 15 24 inch torpedo tubes with five reloads for a total of 20 torpedoes. They were capable of a remarkable 42 knots but their operational range was only 4,000 miles at 18 knots.
The light cruiser situation was even worse. Most of the force were archaic three- and four-funneled cruisers dating from the First World War. Already over 30 years old, these ships were in urgent need of replacement. The only modern light cruisers in the fleet were grossly unsatisfactory designs. The four Agano class light cruisers were 6,600 ton ships but, as one Japanese Admiral was heard to remark "somebody forgot to put guns on them". They were armed with six 5.9 inch L40 low-angle guns in three twin turrets and four 3.9 inch L65 anti aircraft guns in two twin mounts. The 5.9 inch mounts were a lightweight model with limited range and a slow rate of fire. The 3.9s were not the semi-automatic, high rate of fire weapons used on the Type B destroyers but a hand-loaded model. The Aganos were armed with eight 24 inch torpedo tubes (with a set of eight reloads) and 24 25mm anti aircraft guns in eight triple mounts. They also carried a catapult with two seaplanes. They had a speed of 35 knots and a range of 6,300 miles at 18 knots.
The other two modern light cruisers were an even stranger design. Despite displacing 8,100 tons, the Oyodo class were armed with only six 6.1 inch L60 guns in two triple turrets and eight 3.9 inch L65 guns in four twin mounts. The 6.1s were excellent weapons, powerful and long-ranged but the 3.9s were the same slow firing versions as installed on the Agano class. She was capable of 36 knots. The reason for their large size and paltry armament was that the stern half of the ship was occupied by a large hangar and a powerful catapult. This was intended to operate three high-performance floatplanes.
So, the Japanese Navy had, by the middle of 1945, 68 modern destroyers and six new but mediocre light cruisers. The destroyer situation could be lived with in the short term at least. The cruiser situation could not. The light cruisers were the flagships of the destroyer flotillas, they were assigned scouting details and also had to provide screening duties and a host of other minor roles. The existing fleet was capable of none of these things. In 1945, the Japanese Navy decided that they needed to rebuild their light cruiser force. They had little choice in the basis for that rebuild effort; the Agano and Oyodo classes were the only candidates for the new ships.
Type A Class Upgrades
The Type A destroyers presented a particular modernization problems. Although their main batteries were technically dual purpose, they lacked the train rates and elevations necessary for true dual purpose use. They might have been adequate for the 1940s but they could not make a credible claim to a reasonable anti-aircraft defense in the 1950s. Worse, their only other air defense weapons were the obsolete triple 25mm guns. Thus, these ships were essentially without any form of credible anti-aircraft firepower.
Their ASW capability was equally deficient. They, quite literally, had no ability to engage submarines in any manner other than blindly rolling depth charges off their stern. The great difficulty was that these ships were very tight and had no margin for future growth. A limited modernization was carried out in the early 1950s during which their X-turret was removed and four depth charge throwers and two rails were installed aft. A relatively simple sonar set, all that internal volume and hull lines would permit, was also added. This modification essentially brought the ships up to the ASW standard of a British or American destroyer from 1939. The futility of the "modernization" was recognized early and only eight of the Type A destroyers were rebuilt in this manner. Following the Japanese Navy's Strategic Review of 1959-61, it was recognized that the Type A destroyers had no real role left in the fleet and they were withdrawn from service and scrapped.
Type B Class Upgrades
In some ways, the Type B destroyers offered a more hopeful upgrade prospect than the Type A. Their 3.9 inch L65 guns were effective in the anti-aircraft role and their larger hulls offered greater flexibility in rebuilding options. They came in for reconstruction during the mid-1950s, during which they lost X turret in favor of the depth charge throwers and rails and the installation of a search sonar. However, they also received a new lattice foremast with a long range search radar that allowed them to be use d as radar picket ships for aircraft carrier groups. They served in this role until the mid-1960s when they were finally scrapped.
Type C Class Upgrades
About the only thing running for the Type C class destroyers was their speed; other than that they were just a larger and more costly Type A destroyer, sharing all the disadvantages of that type. Accordingly, they remained unmodified until the early 1960s. Under the Japanese Navy's Strategic Review of 1959-61, the coastal defense and inshore anti-ship roles of the Navy were to be taken over by squadrons of missile-armed fast attack craft. These were essentially speedboats armed with two or four anti-ship missiles. They were bereft of any target location or self-defense systems. It was perceived that they would need flagship facilities and the Type C Shimakaze class were seen as ideal for this role. They were built with their two aft sets of torpedo tubes replaced by twin launchers for anti-ship missiles. The bridge structure was extended aft to replace the forward set of tubes, thus providing volume for the required flagship facilities and the mast was replaced by a large lattice structure carrying an air and surface search radar. In common with all the A/B/C class destroyer rebuilds, X turret was removed although no ASW equipment was embarked. The Type C destroyers served in this role until the mid-1970s. By that time, the whole FAC-M concept had been thoroughly discredited and the flotillas fell into disuse.