Weapons Term that Stumped Us: “Pronock”?

We don’t often run into a word referring to weapons that’s completely unfamiliar to us. Even more rarely, we can’t even track the word down. That’s what happened to us in reviewing a 1952 document by the Operations Research Office, a now-defunct FFRDC1 operated by the US Army at the time.

Even generals got in on the tank killing. Of course, this one wound up a POW, out doing a corporal's job with a bazooka.

Even generals got in on the tank killing. Of course, this one wound up a POW, out doing a corporal’s job with a bazooka.

The document reviews the performance of US tanks and tank units in the first year of the Korean War. It was originally classified as SECRET, and the second of two volumes does not seem to have survived. The lost (?) second volume comprised Appendix K to the fundamental document: surveys of some 239 North Korean T-34 tanks examined by American ordnance experts. Fortunately, some conclusions from those surveys made it into the first volume.

But the original document is full of fascinating insights. One of them was that napalm was hugely successful against Nork T-34/85s, and was potentially a threat to American tanks. Napalm is mentioned nearly 60 times in the 308-page report. The mechanism of destruction wasn’t completely certain, but it appeared to be that the nape set the tanks’ solid rubber road wheels on fire, and the burning wheels got hot enough to cook off the rounds in the tanks’ sponsons. FOOM! End of tank, or as tankers say now, “catastrophic loss.” In 1952, the term was “loss, unrecoverable.” That described the situation where the burnt-out hull was here, the insinerated turret was there, and both of them had small, carbonized cinders of what had been the crewmen.

Unknown what killed this tank, but napalm is a possibility. It appears to be buttoned up, but still burning. Tough luck for the Norks inside.

Unknown what killed this tank, but napalm is a possibility. It appears to be buttoned up, but still burning. Tough luck for the Norks inside.

On the basis of limited evidence, air attack accounted for 40 percent of all enemy tank losses in Korea, and 60 percent of all enemy tank losses caused by UN weapons.

On the basis of limited evidence, napalm was the most effective antitank air weapon thus far used in Korea. (p.2).

The difference between all enemy tank losses, and enemy tank losses caused by UN weapons is presumably the same thing that caused a lot of US/UN losses: mechanical failure. A table on p. 36 bears this out, and is discussed on p. 35:

On the basis of this record, the greatest single cause of loss in NK T34’s would seem to be UN air attack, which accounted for 102 out of 239, or about 43 percent of the total losses.

Napalm appears to be the most effective weapon of all, accounting for 60, or about 23 percent of the total count. Abandonments, in most instances without any visible evidence of cause, accounted for 59, almost another 25 percent of the total count. Tank fire was the third largest single cause, knocking out 39 tanks, or about 16 percent. (p. 35).

This led to a discussion of napalm’s effects:

Napalm as a weapon to defeat armor must be given rather special consideration. It is essentially a weapon of an accidental nature. With the possible exception of the relatively rare occurrence of a direct hit, napalm does not of itself destroy or seriously damage a tank. However, it is fully capable of starting a chain of events which may bring about the loss of the vehicle. A napalm bomb, if a hit is registered sufficiently close to the tank, will splash its burning fluid on the tank. Because of the fire, the crew may suffer burns or be induced to abandon the tank. However from the prisoner of war interrogations it appears that tank crews usually had sufficient time to get clear before the fire had spread (see Appendix D). However, the abandonment of the tank ultimately led to its destruction, for the napalm from the first or successive strikes had sufficient time to ignite the rubber on the road wheels, heat the ammunition to the point of detonation, and set fire to the fuel. Any or all of these factors brought about the loss of the tank. (p. 37).

Amplified, and considered in terms of US tanks in this partly redundant passage:

From a general examination of US tanks, the Air Force Operations Analysis tests of napalm against T34 tanks (FEAF Operationr Analysis Office Memo No. 27, prepared jointly with Deputy for Operational Engineering, FEAF, 30 October 1950) and the ORO tank survey (see Appendix K), it is belleved that napalm- caused tank fires are essentially “accidental” in nature, i.e.,
the napalm itself does not have enough energy to set ammunition or fuel afire by bating a tank, but it does have enough effect to set afire rubber bogie wheels , which In turn can fire the tank bilge or amnunition and thus kill the tank. Also, napalm entering through the air intake of a tank can set the bilge afire, again firing ammunition and killing the tank. It appears that both of these “accidents” can be eliminated by minor tank redesign or by fire extinguishing techniques. (p. 59).

Not clear what killed these tanks, but our guess is that the Nork crewman in the foreground suffered a terminal case of amall-arms projectile sickness.

Not clear what killed these tanks, but our guess is that the Nork crewman in the foreground suffered a terminal case of amall-arms projectile sickness.

The USSR may conclude on the basis of the Korean campaign that napalm is a very effective antitank weapon. This possible conclusion can be vitiated by minor redesign of US tanks to reduce effectiveness of “accidental” fires. In future attack on Soviet-manufactured tanks, napalm may remain effective, but the types of fluid filler–such as “G” agents, chlorine trifluoride, or pronock — in improved napalm-type tanks may be even more effective. (p. 60).

There’s the word “pronock.” What is it?

But first, let’s continue our digression into the Korean War tank effectiveness report. The unexpected effects of nape on tanks got the ORO thinking. Some of the thoughts probably explain why the report was classified so highly in the first place:

On the basis of the burning of the rubber on tank road wheels with napalm, resulting in the destruction of the tank, tanks appear vulnerable to 40-kt atomic-weapons attack up to a distance of 2,500 yards on a clear day, and 2,000 yards on a hazy day. (p.3).

Er… yeah. T-34s were vulnerable to destruction by nuking. We’ll accept that.

Original caption: Napalm Bomb Victims.  Mute testimony of accuracy of close support missions flown by Fifth Air Force fighters are these Red Korean tanks, blasted out of the path of advancing 24th Infantry Division units near Waegwan, Korea. AIR AND SPACE MUSEUM#:  77799 AC

Original caption: Napalm Bomb Victims. Mute testimony of accuracy of close support missions flown by Fifth Air Force fighters are these Red Korean tanks, blasted out of the path of advancing 24th Infantry Division units near Waegwan, Korea.

And then there was a list of things that the US ought to develop, based on combat experience with tanks in Korea:

Support a vigorous and expanded research and development program to provide a balanced family of antitank weapons without, however, either overemphasizing or neglecting the role of heavy gun tanks such aa the US T43. This program should emphasize:

a. Development of an effective long-range antitank gun for use by the infantry. This gun should be capable of being moved over rough and unfavorable terrain, preferably in a light, highly mobile vehicle.

That, of course, is the paragraph that gave birth (by a circuitous route, it’s true) to the US M40 106mm recoilless rifle. The M40’s immediate ancestor, the M27, would be rushed to Korea and tested in combat.

b. Development of a family of lethal, influence-fused antitank mines s with sterilizing and arming devices, suitable for remining by rockets, artillery, and air.

Simultaneous development of corresponding mine-detection &vclearing devices.

That stands to reason.

d. Research and development on new types, of air and ground munitions utilizing liquid fillers, such as napalm, chlorine trifluoride, pronock, and G-agents.

That’s the strange use of the strange word, “pronock.” What is it? Napalm is well known. G-agents are nerve agents originally developed by the Germans: Tabun, Soman, Sarin, and Cyclosarin, known in the US/NATO coding system as GA, GD, GB and GF respectively.

Chlorine trifluoride is less well-known, but was a remarkable German “twofer” that produced both incendiary and toxic effects, and that was produced by the Third Reich’s chemical-warfare directorate as “N-stoff” or “Substance N.” The incendiary effect of ClF3 is pretty remarkable — it’s hypergolic not only with normal fuels, but also with water. And it can set asbestos on fire. It does bad things to human beings. It’s never actually been used in warfare (or in most other applications) because containing and handling it is a challenge; Rocketdyne once developed rocket engines that used this stuff as oxydizer with Hydrazine Hydrate as fuel. Hydrazine (N2H4), another Nazi product (as the fuel in the mixture “C-stoff”) used in the V1 and Me163, still has some uses (in the ACES ejection seat, IIRC), but is itself among the nastier things in the hazmat catalogue.

For completeness’s sake, the last of the list of recommendations:

e. Continued development of special amunition, such as shaped-charge and squash-head ammunition, together with improved bazookas and recoilless rifles.

But what in the name of science is “pronock?” It clearly is something that can be used as a tank filler, like napalm, like chlorine trifluoride, like the G-agents. And something that, like those substances, one would rather not have fall on him. Beyond that, we’re stumped. Google was not our friend, either.


Looking for some photos of tank kills definitely attributed to napalm, we found this period article on napalm in Korea which depicts — unfortunately, in a very horribly reproduced half-tone — one of the tests of napalm on a captured T-34. It also describes the thickened gasoline’s composition, and effects on the enemy:

Red tankmen weren’t afraid of diving planes at first, their tough armor would repel 20 mm fire, it was hard to hit the maneuvering tank with rockets, and bombs had to be right on to kill a tank. Napalm was another story. Pilots drop the fire bombs short from low altitude, let it skip to the target. Accuracy is not at a premium. The napalm bomb will cover a pear-shaped area 275 feet long and 80 feet wide. A solid sheet of 1500° fire envelops everything , Killing personnel, exploding ammunition. It is not a flash fire like gasoline alone would be but clings and burns and burns.

… As fast as the Reds moved in tanks to stop the retreat, napalm was dropped on them. They ran out of tanks and weight of phases of the war have seen far fewer communist tanks in action.

The article noted two indirect effects of napalm on the enemy: tanks would be found with the crews inside, unmarked but dead of suffocation, the napalm fires having stolen the very oxygen from the air they breathed. And the psychological effects of the weapon induced many surrenders.


1. FFRDC: Federally Funded Research and Developmant Corporation. The most famous are probably RAND, which was sponsored by the USAF. The ORO was an Army/Johns Hopkins lashup, that the Army grew tired of and pulled the plug on in the 1960s.

15 thoughts on “Weapons Term that Stumped Us: “Pronock”?

  1. Kirk

    I think the “pronock” term you’ve run into refers to what is actually known as “pro-knock” additives, which are the diametric opposite of “anti-knock” compounds added to fuels in order to reduce engine knock. The “pro-knock” agent would be something sprayed on the tank like ether starting fluid, make its way into the air intake for the engine, and then destroying the engine drastically increasing off-cycle fuel detonation in the cylinder…

    I read about this stuff years and years ago in some anti-armor publication, where they discussed the testing of this sort of agent. Initially, they thought they’d be able to kill tank engines pretty easily, but it actually turned out to be a lot like fuel-air explosives: Easy to do in a lab, but damn near impossible to make work out in the field. I think there were a bunch of different compounds tested, all of which contributed to screwing up the combustion cycle in an internal combustion motor via fuel detonation in the cylinders. I think nitromethane might have been one of the agents tested.

    I remember that the idea was to dump a bunch of this stuff onto a tank column or some other tank concentration, while the engines were running, and then watch the engines self-destruct. Hey, presto–Instant mobility kill. Unfortunately, I don’t think they were able to make it work. Like a lot of ideas they come up with…

    Some pan out, some don’t–I’ve always wondered why the hell it took until after Korea before someone wised up and started making “fougasse in a can”, and manufactured Claymore-style devices. Can you imagine the difference that something like a Claymore would have made in the Pacific theater, against Japanese “Banzai” charges? Or, the so-called “human wave” attacks in the Korean war?

    The Claymore was such an obvious idea, you really have to wonder why the hell it took so long to come up with it. Of course, it also took something like 40 years before someone weaponized the Munroe shaped-charge effect, so I guess it shouldn’t come as too much of a shock that nobody noticed the potential uses for an instant fougasse. Yet, someone managed to make a case for trying to develop something like this for anti-tank use, which I have to score as “ludicrously unlikely to work outside of very strictly controlled lab testing”. Freakin’ bizarre.

  2. Thomas McClain

    Adding to the puzzle: My guess is that pronock or (pro-knock) would be the opposite of anti-knock which was tetraethyl lead. The lead was used to prevent pre-ignition, as I’m sure you are aware, so your pro-nock could be a burn rate enhancing compound that liberates oxygen, thereby producing more heat.

  3. whomever

    “The difference between all enemy tank losses, and enemy tank losses caused by UN weapons is presumably the same thing that caused a lot of US/UN losses: mechanical failure.”

    I wonder if logistical failure was also an issue. I’d think that fuel might have been in short supply after Inchon, for example.

    1. Hognose Post author

      Yeah, the report mentions that it’s really hard to conclude which tanks were abandoned because of fuel exhaustion and which were abandoned simply because bugging out was a good idea. One of the real gems in the report is dozens of interview reports with individual Nork tank and logistics soldiers, mostly officers.

  4. Daniel E. Watters

    The US Army wanted to replace the ORO’s director, Dr. Ellis A. Johnson. However, Johns Hopkins University was unwilling to fire Johnson simply because he wouldn’t rubberstamp the Army’s desired conclusions. Thus, the Army and the university mutually agreed to terminate the contract funding for the ORO. After Johnson was shown the door, the Army simply reorganized the ORO as the Research Analysis Corporation (RAC). RAC took over the ORO’s pre-existing projects, property, and most of its former staff. One wag joked that RAC really meant “Relax and Cooperate.”

  5. Stefan van der Borght

    Kirk, I’m hoping the human sluggishness in inventing and implementing novel ways of slaughtering each other is at least a moral pointer in the direction we should actually be striving for…personally, I think we should all agree once and for all that the sword should be the ultimate weapon, and stick to it. Ok, dismembering your opponent is grisly enough for the hollywood depravity merchants, and showplace enough for those that have something martial to prove, but for men of integrity it would be a comfort to know that anyone you just hacked to bits wanted to be there, or you were too unco to avoid; meaning, the warriors die, and the noncombatants have a chance to get out, and no cowardly dronewarrior types get to play. But no, integrity has no place on our battlefield, at least until He gets back and shows us how it’s done, so in the meantime we get to explore the depths of misery. Weps, each time I think I’ve got a handle on things and have developed an overview of applied death, you show me a new facet. Truly you are a Weapons man, and even though I have my concerns with your motivation, primarily spiritual, I can smell enough of the whiff of Expert about you that I’ll continue festering in your presence to learn….and as to the motivational side, even on that score you’re not too far off, certainly close enough to pure to warrant the risk. But still, what swine invented:

    “The incendiary effect of ClF3 is pretty remarkable — it’s hypergolic not only with normal fuels, but also with water. And it can set asbestos on fire. It does bad things to human beings”

    Kudos to the folks that knowingly take the field against that kind of thing, and thank you for the heads up, and for the insight into what might be on opfor menu, and what might be a suitable dish to prepare for them….monkey see, monkey do.

  6. Tennessee Budd

    In the second photo, napalm could be the culprit, but I’d be more inclined to blame the large holes directly below & to starboard of the hull gunner’s position. I imagine the crew compartment was a bit…..messy.

    1. Hognose Post author

      Yeah, I see the hole (looks like a tank-gun hit) now that I look. Note that one of the the extra treads that is on the glacis is kicked up, and it looks like another one might have been blown off.

      Most of the Korean tank engagements were at pretty close range, although there was one at 2,500 or 3,000 meters. Still that was the exception — more common was a knife fight in constricted terrain. The mean was <300 yards. The good news there was that the M4s and M24s didn't need the best ammo to kill T-34s and the superior optics and gunnery of the American tanks really paid off.

      Neither army had spares but the US had a better logistics and recovery-repair operation. Of the tanks knocked out, most American tanks were returned to combat, except the ones lost in the Chosin retreat. Infantry was good at killing tanks at night, but not at permanently destroying them.

  7. Oberndorfer

    Peter Petter-Bowyer, Rhodesia, FranTan.
    Nitrometane fuel was effective, but unobtainium.
    Oxygen deprivaion from a locally produced agent.

  8. Brad

    Fascinating post. What an insight into one aspect of the forgotten war.

    Makes me wonder, how vulnerable are modern wheeled armored vehicles to napalm?

Comments are closed.