The Kongo-class battleships were built between 1911 and 1915 as battlecruisers of a British design. The lead ship of the class, Kongo (1913), was the last Japanese naval ship at that time to be built outside Japan, namely in Great Britain. At the end of the 1920s, all the ships were modernised and hence re-classified as battleships. All ships in the class were lost during World War II. Only Haruna (1915) could be salvaged but was scrapped in 1946.

The Kongo-class battleships were based on a British design for battlecruisers by Sir G. Thurston. For this purpose, Kongo (1913) was built in Great Britain as the last Japanese warship outside of Japan. Over the years, all four ships have been upgraded several times. The first significant reconstructions took place in the late 1920s or mid-1930s, when the battlecruisers were converted into battleships.^[1][2]

The first ship of this class, Kongo (1913), was built in England by the Vickers Shipbuilding Company, whereas the other three ships were built in Japan itself and often from parts manufactured in Great Britain. The ships’ length measured 222.10 meters with a beam of 29.30 meters and a draft of 9.70 meters. The displacement varied between 31,720 tons to 32,156 tons, depending on the ship and its stage in the reconstruction program. The eight to eleven boilers heated four gas turbines, which in turn powered four propellers. This allowed the ships to reach a top speed of 30.5 knots (55.56 km/h). The main armament consisted of four double-barrelled turrets, two forward and two aft, each with two 356 mm / 45 calibre guns. The main secondary armament were fourteen single mounted 152 mm / 50 calibre guns, all equally distributed along each side of the superstructure.^[1][3]

In the mid-1930s, the ships were extensively reconstructed. The length was increased to 225 m, the width to 31.7 m and the draft to 9.8 m. This was all the result of a major adjustment in the armour, among other things. The deck armour was thickened to 96.5-165mm. The ships received new boilers, doubling the capacity to 136,000 shp. The speed therefore increased to approximately 30 knots and the water displacement to approximately 36,000 tons. The armament was also adjusted several times. The main armament remained the same in calibre but was modernised. The secondary armament was reduced to eight, while heavy anti-aircraft guns were added during the Second World War. The number of lighter 25mm / 60 calibre anti-aircraft guns were increased to a total of 100 during the war. As the war progressed, the crew was also significantly expanded, from 1,100 to 1,360, and the ships were classified as battleships. Due to their high-speed capabilities, the ships were usually used as an escort for the aircraft carriers.^[1][4][5]

Two ships, Hiei (1914) and Kirishima (1915), were lost in November 1942 during the Battle of Guadalcanal. Kongo (1913) was lost in November 1944 and Haruna (1915) in June 1945.