The Imperial Japanese Navy battleships of the Ise-class

The Ise-class battleships (IJNS Ise and IJNS Hyūga) were ordered and laid down just as their predecessors - the Fuso-class battleships - were being completed. It was already apparent that the design of the Fusos was imperfect, and the Ise-class battleships were designed to incorporate changes that had been identified as necessary. These included a revised layout for the main armament and a slightly smaller calibre secondary armament.

IJNS Ise as built.

As built, the class's characteristics were as follows:

• Displacement: 31,260 tons (deep load)
• Dimensions:
• Length: 208.18m (683ft)
• Beam: 28.65m (94ft)
• Draught: 8.93m (29ft 4in)
• Propulsion: 24 x Kampon water-tube boilers providing steam to 4 x steam turbines, each driving a propellor
• Speed: 23 knots
• Range: 9,680 nautical miles at 14 knots
• Complement: 1,360
• Armament: 6 × twin 356mm (14-inch) guns; 20 x single 140mm (5.5-inch) guns; 4 x single 76.2mm (3-inch) anti-aircraft guns; 6 × 533mm (21-inch) torpedo tubes
• Armour: Belt: 300mm (11.8-inch); Deck: 85mm (3.3-inch); Gun turrets: 254mm (12-inch); Barbettes: 305mm (12-inch); Conning tower: 305mm (12-inch)

IJNS Ise during the mid 1920s.

From 1934 to 1937 the class was reconstructed.

• The stern was lengthened by 7.62 meters to improve speed.
• The forward superstructure was rebuilt into a pagoda mast.
• Torpedo bulges were added for better underwater protection.
• With the exception of the rearmost turret, main battery's elevation was increased to 43 degrees for improved range.
• The number of casemate-mounted 5.5-inch/140mm guns was reduced from twenty to sixteen.
• The existing single 3-inch/76.2mm anti-aircraft guns were replaced by four twin 5-inch/127nn anti-aircraft guns.
• Ten twin-mounted 1-inch/25mm Hotchkiss anti-aircraft machine guns were fitted. 
• Additional armour was added to the deck and turret tops and two torpedo bulkheads were installed, increasing the ship's overall armour protection.
• The existing twenty-four mixed coal-fired and oil-fired water-tube Kampon boilers were replaced by eight lighter and more powerful oil-fired Kampon boilers.
• The fore funnel was removed and the remaining funnel was rebuilt in a different position.
• Newer, lighter steam turbines were fitted in place of the original geared turbines.

After their 1930s reconstruction, the class's characteristics were as follows:

• Displacement: 42,001 tons (deep load)
• Dimensions:
• Length: 216m (708ft 8in)
• Beam: 31.75m (104ft 2in)
• Draught: 9.45m (31ft)
• Propulsion: 8 x Kampon water-tube boilers providing steam to 4 x steam turbines, each driving a propellor
• Speed: 25 knots
• Range: 7,870 nautical miles at 14 knots
• Complement: 1,376
• Armament: 6 × twin 356mm (14-inch) guns; 16 x single 140mm (5.5-inch) guns; 4 x twin 127mm (5-inch) anti-aircraft guns; 10 x twin 25mm anti-aircraft guns
• Armour: Belt: 300mm (11.8-inch); Deck: 140mm (5.5-inch); Gun turrets: 254mm (12-inch); Barbettes: 305mm (12-inch)
• Aircraft: 3 x floatplanes; 1 x catapult

IJNS Ise after her first major reconstruction.

After the loss of four aircraft carriers at the Battle of Midway. the Imperial Japanese Navy examined the possibility of converting existing battleships in to aircraft carriers. This was felt to be both too expensive and would take too long, but as IJNS Hyūga had lost her No.5 turret after an explosion and the No.6 turret of both ships was unable to elevate to 43 degrees like the rest of the main armament, conversion into hybrid battleship/aircraft carriers was viable.

During the reconstruction, the following changes were made:

• Nos.5 and 6 turrets and their supporting structures were removed and the holes in the ships structure was plated over with 152mm/6-inch armour.
• The existing 140mm/5.5-inch secondary armament was removed.
• Four additional twin 127mm/5-inch anti-aircraft guns were added.
• The existing ten twin 25mm anti-aircraft guns were replaced by nineteen triple 25mm anti-aircraft guns. Twelve triple and ten single 25mm anti-aircraft guns were later added.
• A 70m/229ft 8in long and 29m/95ft 2in to 13m/42ft 8in wide flight deck was built atop a 40m/131ft 3in long and 20m/65ft 7in to 11m/36ft 1in wide and 6m/19ft 8in high hanger at the stern of the ship.
• Two catapults were fitted at the forward end of the flight deck.

After their conversion into hybrid battleship/aircraft carriers, the class's characteristics were as follows:

• Displacement: 42,675 tons (deep load)
• Dimensions:
• Length: 219.62m (720ft 6in)
• Beam: 31.71m (104ft)
• Draught: 9.03m (29ft 8in)
• Propulsion: 8 x Kampon water-tube boilers providing steam to 4 x steam turbines, each driving a propellor
• Speed: 25 knots
• Range: 7,870 nautical miles at 14 knots
• Complement: 1,463
• Armament: 4 × twin 356mm (14-inch) guns; 8 x twin 127mm (5-inch) anti-aircraft guns; 31 x triple & 10 x single 25mm anti-aircraft guns
• Armour: Belt: 300mm (11.8-inch); Deck: 85mm (3.3-inch); Gun turrets: 254mm (12-inch); Barbettes: 305mm (12-inch); Conning tower: 305mm (12-inch)
• Aircraft: 22 x aircraft; 2 x catapults

IJNS Ise after her reconstruction into a hybrid battleship/aircraft carrier.

---

The class's wartime service:

• December 1941: Formed part of the distant force covering the retirement of the aircraft carrier that attacked Pearl Harbour.
• February to November 1943: Converted into hybrid battleship/aircraft carriers.
• October 1944: Battle off Cape Engaño.
• November 1944: The catapults were removed and the ships were used to transport troops and supplies.
• March 1945 onward: The ships were used as floating anti-aircraft batteries..
• July 1945: The ships were sunk by US Navy carrier-borne aircraft.