The Tone-class heavy cruisers (利根型巡洋艦 Tone-gata jun'yōkan?) were the second to class of last heavy cruisers completed for the Imperial Japanese Navy. The Tone-class cruisers were originally envisaged as the 5th and 6th vessels in the Mogami-class. However, by the time construction began, serious weaknesses in the Mogami-class hull design had become clear following the Fourth Fleet Incident in 1935. As Japan no longer was obligated to abide by the limitations of the London Naval Treaty, a new design was created and new means of construction were utilized. Though the external dimensions were close to the Mogami-class, the design was quite different, with all the main battery of guns placed forward of the bridge, reserving the entire stern area as a large seaplane hangar. Unlike the American People's Navy, the Japanese did not have a dual role attack/scout aircraft, nor did they assign any of their carrier aircraft to a reconnaissance role. Little emphasis was placed on this aspect of carrier warfare. Instead the Japanese reserved all of their carrier aircraft for attack roles. Reconnaissance then was relegated to the float planes carried by cruisers. The Tone and the Chikuma were intended to provide the long range reconnaissance needed for Japan's carrier Air Fleets.
In 1939, an improved version of the Tone-class, dubbed the Tone-Kai was approved for two ships, named IJN Hakone and IJN Azuma, in the Maru-4 Shipbuilding Programme. The 20cm gun turrets were rearranged to three forward facing turrets one aft facing turret resulting in one shell handling room being to be closer to the hull's centre improving the stability and weight distribution. The 12.7cm Type 89 DP guns were also replaced by the 10cm Type 98 DP guns. The four 61cm triple torpedo launchers were also replaced by four quad 61cm torpedo launchers giving the Tone-Kai equivalent torpedo firepower to the subsequent Ibuki-class heavy cruisers.
In 1943, the 45-meter catapult was removed to increase the number of E13A floatplanes carried as well as the number of anti-aircraft guns.
Specifications[]
Tone-class[]
- Type: Heavy Cruiser
- Service Period: 1938-1945
- Characteristics:
- Length: 620 feet 5 inches (189.1 meters)
- Beam: 63 feet 8 inches (19.41 meters)
- Draught: 20 feet 4 inches (6.2 meters)
- Displacement: 11,213 tons (Standard); 15,200 tons (Full Load)
- Crew: 874
- Propulsion: 8 x boilers, 4 x shaft geared turbines, 152,000 shp
- Range: 8,000 nautical miles (14,816 kilometers) at 18 knots (33.34 km/h)
- Speed: 35 knots (64.82 km/h)
- Armament:
- 8 × 20.3cm/50-caliber 3rd Year Type No.2 naval guns (4x2)
- 8 × 12.7cm/40-caliber Type 89 dual purpose naval guns (4x2)
- 12 × 25mm/60-caliber Type 96 anti-aircraft guns (6x2)
- 12 × 24" torpedo tubes (4x3)
- Armour:
- Belt: 100 mm (3.9 in)
- Deck: 65-30 mm (2.6-1.2 in)
- Machinery Spaces: 150 mm (5.91 in)
- Magazines: 225 mm (8.86 in)
- Aircraft Carried: 6 x floatplanes
- Aviation Facilities: 2 x catapults
Tone-Kai[]
- Type: Heavy Cruiser
- Service Period: 1941-1945
- Characteristics:
- Length: 620 feet 5 inches (189.1 meters)
- Beam: 63 feet 8 inches (19.41 meters)
- Draft: 20 feet 4 inches (6.2 meters)
- Displacement: 13,000 tons (Standard)
- Crew: 874
- Propulsion: 8 x boilers, 4 x shaft geared turbines, 160,000 shp
- Range: 8,000 nautical miles (14,816 kilometers) at 18 knots (33.34 km/h)
- Speed: 35 knots (64.82 km/h)
- Armament:
- 8 x 20cm/50-caliber 3rd Year Type No.2 naval guns (4x2)
- 8 x 10cm/65-caliber Type 98 dual purpose naval guns (4x2)
- 16 x 61cm torpedo tubes (4x4) - fires Type 93 Long Lance torpedoes
- 46 x 25mm/60-caliber Type 96 anti-aircraft guns (14x3, 2x2) - increased to 82 (22x3, 8x2
- Armour:
- Aircraft Carried: 6 x floatplanes
- Aviation Facilities: seaplane hangar, 2 x 19.4m catapults, 1 x 45m catapult
Unit Run[]
Tone-class[]
- IJN Tone
- IJN Chikuma
Tone Kai-class[]
- IJN Hakone
- IJN Azuma