The Japanese Ontos?

Having discussed the Marines’ Ontos, seems only fitting to mention a very similar vehicle built at around the same time in Japan.

Type 60 Self Propelled Anti-Tank Gun

The Type 60 Self-Propelled Anti-Tank Gun (SPAT) evolved from an early 1950s requirement for the Japanese Self Defense Forces.  Emphasis on DEFENSE.  During the Korean War, the United States encouraged Japan to form a military force to defend the island nation.  The most likely threat in any conventional war was an amphibious or airborne force landing to secure the various straits connecting Russian or Chinese harbors to the Pacific sea-lanes.  As such, the Japanese needed a highly mobile force to contain a moderately armored opponent.  Requirements called for light-weight vehicles capable of rapid transport by train.  Doctrine stressed ambush type tactics to contain then throw back enemy invasions.  Concurrent projects pursued a main battle tank and a self-propelled anti-tank weapon optimized for Japanese requirements.  Both projects proceeded with some deliberation through the 1950s.

SS1-Revised Prototype with Four Rifles

SPAT prototypes from Komatzu Manufacturing (identified as MI or SS1 in some sources) and Mitsubishi Nippon Heavy Industries, Ltd (noted as MII or SS2) rolled out in 1956.  The Komatzu offering used a front mounted 105hp diesel engine, while the Mitsubishi had a 110hp engine in the rear of the chassis.  Both featured two 105mm recoilless rifles (a Japanese derivative of the US M27 recoilless rifle) in a limited traverse mounting.  After testing, Komatzu delivered an additional prototype, the SS1-Revised, with four 105mm rifles.  Mitsubishi delivered the SS-3 with five road wheels.  Then a fourth experimental batch named SS-4, with two M40 106mm Recoilless Rifles (same as used on the M50 Ontos), arrived.  The SS4 also used a more powerful 6-cylinder 150hp diesel engine, mounted in the front.  This emerged as the optimum configuration, and entered series production in 1960 as the Type 60.  In some regards, the Type 60 hearkened back to the “Tankettes” of the 1930s.

Comparison of Production Type 60 (left) and SS1-Revised (right)

Just like the Ontos, the Type 60 used .50-caliber spotting rifles to aid the aim of the main guns.  Also like the Ontos, the Japanese SPAT had a crew of three – commander, loader, and driver.  But unlike the Ontos, the Type 60’s rifles sat in a retractable turret to reduce the vehicle’s height.

Type 60 Self Propelled Anti-Tank Gun

When retracted, the turret traversed only 10 degrees left or right, with an elevation of 10 degrees and depression of 5 degrees.  Deployed in the firing position, traverse increased to 30 degrees, elevation to 15 and depression to 10.

Front View of Type 60

Note also the part welded and riveted construction. The front hull was sloped somewhat, but the sides were vertical. Overall, protection matched that of the Ontos, with only 12mm of armor to defend against small arms and artillery fragments.

Rear View of Type 60

Ammunition lockers provided six rounds. And like Ontos, the crew had to dismount to reload after firing. (And go to Toadman’s Tanks for a good walk-around of the Type 60.)

Type 60 in the Snow

In the field, the eight ton Type 60 reached 34 mph on roads. Turret retracted, the SPAT stood only 4.5 feet tall. Just over 7 feet wide and 12 feet long, the Type 60 was a compact fighting vehicle.

Type 60 During Training Exercises

Komatsu produced over 250 Type 60s.  After the initial “Type A” production, “Type B” appeared with some structural reinforcements.  In 1974 a “Type C” entered production using a liquid-cooled engine with the same power ratings. The only other major modification considered was an auto-loader.  But that was quickly dismissed as overly complicated for the small vehicle.  As late as 2001, 140 of these SPATs remained in service.  But officially all were retired in 2008.

Type 60 on Maneuvers in 2006

Normally, I’d close out with a video or two.  But the only clips I could find feature this guy:

Occasional movie appearances were the highlight of the Type 60s service.

One might easily dismiss the Type 60 as a “knock-off” of the Ontos.  I wouldn’t be so quick.  As mentioned before, the Ontos sprang from US Army requirements for an airborne anti-tank weapon system, only later to see service as a lightweight anti-tank system for the Marines.  Designers optimized the Ontos with enemy counter attacks against envelopment operations (fancy way of lumping airborne and amphibious assault into one category).  In Japan the Type 60 was the defender countering just such envelopment.

As often occurs with weapons development, dissimilar requirements lead to very similar weapon systems.

SPAT the Scorpion

Here’s one of my favorite types from the “long forgotten” fighting vehicle files – the M-56 Self Propelled Anti-Tank (SPAT) Gun, nicknamed the “Scorpion.”

M90 Scorpion 3
M-56 Scorpion - Front Quarter

This example was on display at the Infantry Museum at Fort Benning (the museum has since relocated, and I don’t know if they have moved all the outdoor exhibits yet).  First impression …. is this really a fighting vehicle?  Looks more like a toy.  Despite the looks, this tracked vehicle was rather formidable in its day.

The Army developed the M-56 based on post-World War II requirements for a light anti-tank weapon for airborne forces.  Everyone recalls the limited effectiveness of the bazooka on German Tiger tanks.  Post war, the Army feared more potent Soviet tanks would blunt airborne operations.  In the late 1940s and early 1950s, towed anti-tank guns capable of dealing with heavy tanks weighed too much for light infantry use.  ATGMs, while promising, were still in development at that time.  One option was a lightweight anti-tank gun carrier – an extreme version of the World War II tank destroyer.

Designers built the M-56 around a 90mm gun, which for all purposes was the same gun arming contemporary M-47 medium tanks.  Following every effort to save weight, the Scorpion offered no protection for the crew save a blast shield around the gun.  Note the bare metal seat above the equipment bin, just below the gun.  Had to be good for the old fourth point of contact!

M56 scorpion 1
M-56 Profile

All dressed out, the M-56 weighed just over 7 tons.  A 200-hp gas engine gave it a road speed of 28 mph.  Note the road wheels in the side view.  Those are pneumatic run-flat wheels, which no doubt eased the ride for the crew of four in the bare metal seats.

The M-56 carried 29 ready rounds into action, stowed in tubes under the gun.

M90 Scorpion 2
Ready Rounds

The obvious drawback was lack of crew protection.  Also with a powerful gun on a light chassis, the M-56 kicked considerably, requiring some forethought in weapon placement.

But the Scorpion was what the Army needed at the time – a light weight anti-tank system capable of supporting airborne operations.  Cargo planes of the day could handle the light load.  As seen in this clip, the M-56 required six chutes.  Watch the drop:


The M-56 entered service in 1953 with the 82nd and 101st Airborne Divisions.  The 173rd Airborne Brigade used the Scorpions in Vietnam.  But by the late 1960s, the multi-purpose M-551 Sheridans supplanted the M-56 in the airborne units.

Now before we go off criticizing the 90mm SPAT as a bad weapon system, consider the time frame and technology.  Further consider the opposition, over behind the Iron Curtain, were fielding things like the ASU-57 and ASU-85.  So if our weapons were silly, we were all silly together!

More photos of the M-56 are at David Lueck’s walk around page.