In the mid-1950s, the Japanese Ground Self-Defence Force issued a requirement for a full-tracked armoured personnel carrier. Development began in 1956 with overall control of the project managed by the Technical Research and Development Headquarters of the Japanese Self-Defence Agency. In 1957, prototypes of the APC were completed by Komatsu and Mitsubishi. The Komatsu prototype was called the SU-I and the Mitsubishi model the SU-II.

Both prototypes weighed 10.6 tonnes, carried nine men and had a maximum road speed of 45 km/h. Between 1957 and 1958, the SU-I and SU-II were tested alongside a US-supplied M59 APC. Eleven second-series prototypes were manufactured by Mitsubishi Heavy Industries and the Komatsu Manufacturing Corporation. Mitsubishi built five SU-II (Kai) Ms, one SV (Kai) M and one SX (Kai) M, M standing for Mitsubishi and Kai for modified. Komatsu built two SU-II (Kai) Ks, one SV (Kai) K and one SX (Kai) K, K standing for Komatsu. The SV was the 81 mm mortar carrier and the SX was the 107 mm (4.2 in) mortar carrier.

In both, the mortar was mounted in the rear compartment but on the SX the top of the hull was sloped to the rear to avoid muzzle blast from the 107 mm mortar.

In July 1959, four prototypes of the SU-II (Kai) were completed and tested through to October 1959. In 1960 the vehicle was standardised as the Type 60 APC, with the mortar carriers standardised as the Type 60 self-propelled 81 mm mortar and the Type 60 107 mm (4.2 in) mortar.

The first production contract for 24 vehicles was provided for in the 1959 budget and production was undertaken by Komatsu and Mitsubishi. Final orders were placed, with funding from the 1972 Budget.

As increasing numbers of the more recent Type 89 MICVs enter service with the Japanese Ground Self-Defence Force, older Type SU 60s will be progressively phased out of service as by today's standards they are obsolete. It is understood that by mid-2007 only about 30 Type SU 60 series APCs remained in service. Description

The hull of the SU 60 APC is made of all-welded steel which provides the occupants with protection from small arms fire and shell splinters, with the driver seated at the front of the hull on the right. The driver has a single-piece hatch cover that opens to the right over his position, in front of which are three M17 day periscopes. The bow machine gunner sits at the front of the hull on the left and has a single-piece hatch cover that opens to the left rear, with an integral M6 day periscope for aiming the 0.30 (7.62 mm) M1919A4 bow machine gun.

The commander sits immediately behind the driver's and bow machine gunner's position and has a single-piece hatch cover that opens to the left rear. The eight vision blocks provide all-round observation for the commander.

The Mitsubishi V-8 diesel engine is on the left side of the hull to the rear of the bow machine gunner and power is transmitted to the differential at the front of the hull by a short propeller shaft.

The gunner sits to the rear of the commander on the right side of the hull and has a two-piece hatch cover that opens either side of his position. The 0.50 (12.7 mm) M2 HB machine gun can be traversed through a full 360° and is provided with a shield.

The troop compartment is at the rear of the hull with the six infantrymen seated on individual seats, three down each side of the hull. They enter and leave the vehicle by two doors in the rear of the hull that open outwards. The right door has a small observation slit. Over the top of the troop compartment is a single-piece hatch cover that opens forwards. To the rear of this is a two-part hatch cover that opens either side of the hull. Each part of the hatch cover is in two halves, hinged in the centre. There is no provision for the infantry to use their small arms from inside the vehicle.

The torsion bar suspension either side consists of five dual rubber-tyred roadwheels with the drive sprocket at the front, idler at the rear and three track-return rollers. The first, second and fifth roadwheel stations are provided with a hydraulic shock-absorber. The SU 60 APC does not have an NBC system, nor any night vision equipment or amphibious capability. Variants

This is essentially a Type 60 APC with an 81 mm mortar mounted in the back of the hull firing to the rear with two doors in the rear of the hull. A bipod and baseplate are carried on the glacis plate, enabling the 81 mm mortar to be deployed away from the vehicle. The 81 mm mortar has an elevation of +40 to +85°, a traverse of 40° left and right and a maximum range of 3,000 m. The SV 60 carries 24 mortar bombs. It has a crew of five and weighs 12,100 kg fully loaded. Armament consists of one roof-mounted 0.50 (12.7 mm) M2 HB (0.50) anti-aircraft machine gun. Only 18 of these vehicles were built.

This has a 4.2 in (107 mm) mortar mounted in the rear of the hull firing to the rear. A baseplate and stand are carried on the glacis plate, enabling the 107 mm mortar to be deployed away from the vehicle. The 107 mm mortar has an elevation of +37 to +65°, a traverse of 40° left and right and a maximum range of 4,000 m. Eight mortar bombs are carried. The SX 60 has a crew of five, weighs 12,900 kg fully loaded but is fitted with the 0.50 (12.7 mm) M2 HB anti-aircraft machine gun only. It can be distinguished from the 81 mm mortar carrier by the lack of a bow machine gun and the distinct chamfer to the rear of the top of the hull of the Type SX 60. The SX 60 has a single-piece ramp at the rear of the hull, hinged at its lower part. Only 18 of these vehicles were built. This has now started to be replaced by the Type 96 120 mm (8 × 8) self-propelled mortar system, details of which can be found in a separate entry.

A small number of Type SU 60 APCs were fitted with Mitsubishi KAM-3D wire-guided anti-tank missiles in their launcher boxes, one on either side of the hull top rear.

There are at least three other variants of the Type SU 60 APC, an NBC detection vehicle, a dozer and a model modified to resemble the Russian BMD-1 airborne combat vehicle used by the Japanese Ground Self-Defence Force for training purposes. Only two dozers are in service, used by the 7th Division for clearing snow. A prototype of a 105 mm self-propelled howitzer was built under the designation SY 60 but was never placed in production.