[Webstral]

I agree that there are reasons why assault guns aren’t generally included in the lineup of the major powers’ AFV park, just as there are reasons why the assault gun joined the lineups of the Wehrmacht and Red Army. Cost is a factor for the emergence of the assault gun; without a gun turret, the fighting vehicle is cheaper and less complex. Also, a heavier gun can be mounted for the same weight of vehicle. Cheapness and ease of maintenance are important factors, after all.

Another reason for the emergence of the assault gun is the tendency for the tanks to fight each other instead of supporting the infantry. The British (and perhaps the French—I can’t remember anymore) distinguished between cavalry and infantry tanks. The former were light, fast machines meant to exploit breakthroughs and beat up rear-area units. The M4 Sherman with its 75mm gun is a splendid example of such a tank. Infantry tanks were slower and heavier with better armor and (sometimes) better guns than their cavalry counterparts. The infantry tank was intended to fight in direct support of the infantry, although obviously a big heavy mike foxtrot is going to get drawn into tank-on-tank combat as the opportunity arises. The assault gun is a natural evolutionary development of the infantry tank concept. In my opinion, the assault gun is a good marriage of economy and specialization. (Take my opinion on such things with a grain of salt—I’m no tanker.)

There are some arguments against assault guns, and many of these arguments have merit. On a fast-moving battlefield, the assault gun with its limited traverse is at a distinct disadvantage against MBT that can shoot on the move. If the Soviets are to be believed, and if Operation Desert Storm is any indicator, meeting engagements are sufficiently common to be as normal as deliberate attacks and defenses. The jury’s still out on what a really large-scale mechanized war between comparable armies would look like. A howitzer on an assault gun, which will have a fairly limited direct fire range (1,500 meters?) is at a very distinct disadvantage against a wide variety of ATGM. Although the frontal armor of an assault gun can be thickened vis-à-vis the frontal armor of a tank with the same chassis, it may or may not be practical to provide sufficient protection against all or most ATGM. A tank certainly can provide direct fire support to the infantry. IFV can provide direct fire support, though I don’t know how a 25mm autocannon stacks up against a 105mm piece in terms of servicing hardened targets. How many rounds of 25mm does one have to fire at a hardened target to achieve a knockout blow that could be achieved with a single round of 105mm HE or HESH?

The Soviets included HE in the basic load for their MBT. When I was Regular Army in the 1990’s, the question was being asked whether the combat load for the M1 wasn’t a bit too specialized. At the time, the M1 carried sabot rounds and HEAT. There were three machine guns for AP, but there were no rounds specifically for infantry support. I know that in the interim more attention has been paid to providing the infantry with direct support that extends beyond beating up the enemy’s AFV (the value of which is never to be underestimated). However, the US would have entered the Twilight War with an MBT incapable of providing exactly the kind of fire for which the assault gun is intended.

One of the problems with the fast-moving modern battlefield is that it leaves behind pockets of enemy resistance. If all goes well, the next echelon or the echelon after that deals with the problem. This is an ideal circumstance under which to use an assault gun. Behind the front, the assault gun shouldn’t have to deal with enemy tanks—at least not in the same numbers one would expect to find them at the front. AT guns and ATGM probably will be present in bypassed enemy units, although obviously the size and composition of bypassed enemy units will vary considerably. Still, mopping up pockets of resistance is a job for the infantry and fire support vehicles. There’s no need for a high-performance fighting vehicle like the M1 to operate in direct support of dismounted infantry. I’d argue that detailing an M1 for this job is wasteful, though the US Army certainly has done enough of it over the past decade. By the same token, detailing an SP gun for this job is wasteful. A 155mm cannon certainly can deliver effective fire against enemy strong points, but the field artillery has plenty of other work to do during an offensive. Man portable weapons lack the range to go after targets that an assault gun with a 105mm howitzer can tackle. Also, man portable weapons like the AT-4 tend to be specialized for the anti-armor role. HEAT warheads are less effective in the bunker busting role than an HE or HESH round of equal diameter because much of the round’s energy goes into creating a plasma bolt. A plasma bolt has lesser effects inside a bunker than inside an MBT for a couple of reasons. The first is that there is lot less combustible material (fuel and ammunition) inside a hardened infantry fighting position than inside an AFV. The second is that while the plasma bolt will create spalling on the interior of a concrete or wooden bunker, the overall impact is lesser. When one is tackling a small cinder block structure, this doesn’t matter so much. But the Israelis have noted that a HEAT round from an MBT doesn’t always do the job against enemy combatants inside ordinary civilian dwellings, although the plasma bolt may penetrate multiple walls. HE or HESH in 105mm, on the other hand, is well-suited for tackling hardened structures and killing or disabling the troops inside. This is a good job for an assault gun.