The Mogami was a Japanese cruiser launched in 1934, leading ship of the homonym four-ship class. Initially conceived as light cruisers armed
with 155-millimeter cannons, they were later rearmed with 200-millimeter cannons and reclassified as heavy cruisers. The ships of the Mogami
class had a powerful antiaircraft battery, two catapults with three aircraft and four 610-millimeter torpedo triple launchers with reloads.
They could as well achieve the very high speed of 37 knots, however at expenses of operational range.
Despite the zeal put into saving weight, by means of using welding extensively, the displacement largely exceded the limit of 10160 tonnes
imposed by the Washington Naval Treaty. But the worst was that this constructive method was the source of structural weaknesses that arose
during the artillery tests. The two first ships of the class, Mogami and Mikuma, were sent to Kure to be rebuilt whereas the other two, Kumano
and Suzuya, were modified while they were still being built. These works were used as well to improve other aspects of the ships.
Stability could be improved by increasing the beam with additional bulging and the antiaircraft armament was increased.
In 1939 the triple 155-millimeter turrets were replaced by twin 200-millimeter turrets and additional armor was installed outside the bulges,
which further increased the beam to up to 20.2 meters. Four of the 155-millimeter turrets suppressed were destined to the battleships Yamato and
Musashi. In the end, the Mogami class was integrated by excellent ships, powerfully armed and able to withstand a great amount of damage, fast
and with a good operational range, but the quality could have been better if the project had not been based on a too limited displacement.
The Mogami resulted severely damaged during the Battle of Midway and remained in reparation until April 1943. But during the reparations the
original cruiser was transformed in a seaplane carrier, being the aft turrets replaced by a clean deck to manage the aircraft. The illustration
shows the key differences between the original cruiser of 1939 and the reconstruction, which included as well a very enhanced antiaircraft battery and
revised electronics with the addition of an exploration radar in the top of the mast. The Mogami resulted severely damaged and disabled during
the fatidic "Night of Surigao" and she was finally sunk by the Japanese destroyer Akebono.
Class: Mogami (4 units - Kumano, Mikuma, Mogami, Suzuya)
Type: Heavy cruiser
Length: 201.6 meters as built; 201.5 meters in 1939
Beam: 18 meters as built; 20.2 meters in 1939
Draught: 5.4 meters as built; 5.8 meters in 1939
Displacement (standard): 8500 tonnes as built; 12598 tonnes in 1939
Propulsion: 4 x shaft, 4 x steam turbine, 10 x boiler Kampon, 152000 horsepower
Speed: 37 knots (68.5 kilometers/hour) as built; 35.5 knots (65.7 kilometers/hour) in 1939
Range: 6726 nautical miles (12456 kilometers) at 14 knots as built
Complement: 850 as built
Armament (as built): 15 x 155-millimeter 55-caliber cannon, 8 x 127-millimeter 40-caliber cannon, 4 x 40-millimeter cannon,
12 x 610-millimeter torpedo tube, 3 x aircraft
Armament (in 1939): 10 x 200-millimeter 50-caliber cannon, 8 x 127-millimeter 40-caliber cannon, 8 x 25-millimeter cannon,
4 x 13-millimeter machine gun, 12 x 610-millimeter torpedo tube, 3 x aircraft
Armament (in 1943): 6 x 200-millimeter 50-caliber cannon, 8 x 127-millimeter 40-caliber cannon, 30 x 25-millimeter cannon,
12 x 610-millimeter torpedo tube, 11 x aircraft
Armor: 100-125 millimeters in belt, 127 millimeters in magazines, 35-60 millimeters in deck, 25 millimeters in main turrets