Craig’s recent posts on the SPAT and the Ontos build on an earlier post I did on the M551 Sheridan armored vehicle. All these vehicles had a common heritage. They tried to find a practical combination of mobility, firepower, and protection that could give light and airborne forces greater firepower on the battlefield, while still being small enough to be delivered by air.
Weight is always a critical issue for the designers of armored vehicles. But when you need to be able to drop those vehicles by parachute, it is even more critical. There’s a very finite limit on the amount of lifties an airplane can generate, and trying to get a C-130 to lift more than that will only lead to disaster. And there are so few other airlifters in our fleet, designing an armored vehicle that can only be lifted by C-5s or C-17s severely limits its air-drop utility.
This isn’t a new problem. Almost from the very first days of airborne operations, planners have struggled to match the strategic and operational mobility of airborne forces to firepower that was strong enough to keep them from being swept off the battlefield by conventional forces. The very first airborne units in our Army were limited to small arms, machine guns, and some light mortars. They were superbly trained, but would not have lasted long against determined enemy opposition. By D-Day, US Airborne Divisions had some light artillery and some light anti-tank guns, but no real armor. They were restricted by the lifting capacity of the C-47, which was suitable only for troops and bundled cargo, and the gliders of the time, the Waco CG-4 and the British built Horsa. The British also designed the Hamilcar glider to carry a light tank designed specifically for airborne forces, the M22 Locust. The Locust never saw combat with American forces, and only the slightest service with British forces. It was not considered a success.
But the problem of armored firepower for airborne and light forces had not disappeared. It continued to plague planners in the post-war years.
The British 1st Airborne Division had learned the hard way that lightly armed airborne troops could not attack into the face of armored formations. US planners had learned from that, and sought a way to bolster the strength of airborne forces. The results were mixed at best.
Craig did an admirable job of describing the M56 Scorpion which offered good firepower and mobility, but no protection. And he also described the M50 Ontos, which also struggled to find a balance between firepower, mobility and protection. Next in line was the M551 Sheridan. Like the other vehicles mentioned, it was not entirely successful. It wasn’t a complete failure, mind you. But it suffered from the compromises that had to be made to meet very stringent weight requirements.
So it stood for a long time that the Sheridan was the only armor for the airborne forces. Eventually, old age took its toll on the fleet, and the Sheridans were due for a well earned retirement. The question became, what to replace the with? At the same time, the Army was looking to increase its strategic mobility by converting one of its two active cavalry regiments to a lighter formation that could be moved primarily by air. The 2nd Armored Cavalry Regiment traded in its tanks and Bradleys for lightly armored (and lightly armed) Humvees. This made the unit easier to move, but again, it was pretty light on staying power. The Army took another crack at coming up with an air transportable armored vehicle.
Eventually, after running through a couple different acronyms and the usual program shenanigans, the contractor presented to the Army the XM8 Buford Armored Gun System. It it one of the few vehicles that could honestly be described as a light tank. It was fully tracked, had a 105mm main gun, and was actually fairly small. And it was light enough to be transported and airdropped from C-130 aircraft.
Now, as always, there is the pressure of weight constraints to be balanced against the vehicles vulnerability to anti-armor weapons. In order to get the M8 weight down to a level that would fit onto a C-130, they had to accept very thin armor, barely enough to stop small arms fire and some artillery fragments. That meant the M8 would be very, very vulnerable to any anti-tank weapons. The solution to that problem was bolt on armor. Normally, any armor on a vehicle actually forms an integral part of the hull, and is part of the load bearing structure. But for the M8, the contractor came up with two additional levels of armor that could be bolted on in the field with simple hand tools, and increase the protection of the vehicles. For instance, the 82nd might be forced to drop in someplace unpleasant, and to drop, would have to accept the risk of going in with just the lightest armor. But as soon as possible, the additional kits of armor could be flown in and applied. The M8 would never have the level of protection that an M1 Abrams would have, but it would be a good deal better armored than either an M551 or any Humvee.
The development of the M8 was actually fairly smooth (compared to a lot of programs, at least) and the vehicle had just been accepted for service and was just about to be placed in series production when the entire program was cancelled. What happened you ask?
Well, in 1996, the President and the Secretary of Defense told the Army they were going to cut end-strength another 20,000 troops for the Army. The Army was aghast at the cuts, and asked if they could keep some of those troops if they found other savings. And one of the easiest ways to save money was to NOT spend a billion or so on buying the M8. The deal was made. Eventually, the Sheridans were withdrawn, and the 82nd was without any armor.
With the advent of the Stryker brigade, we’ve seen (and written about) the Stryker MGS or Mobile Gun System. It fulfills much the same role as the M8, but has less armor capability. Nor is the Stryker expected to be airdropped. It is, however, expected to be moved by air, in addition to surface shipping. The same challenges of balancing protection, mobility, and firepower are still with us.