Light tanks for the beligerents

[Shortround6]

No takers?
The light tank was deemed to be a good thing even by Cold war armies, many of them building and/or operating them. No light tanks should find itself going against the established front line, I agree with that. Anyway, since those were built operated in ww2, why not proposing something that is better than what was fielded, yet suited to be produced at the factories unfit to build 30+ ton 'proper' tanks. We don't have to call them 'light'. 'Tanks' will do

The post war "light tanks" were built for special purposes for the most part. The Russian PT-76 was an amphibious reconnaissance vehicle. The British Scorpion was also a reconnaissance vehicle, more of a tracked armored car. The French AMX-13 was more of a tank destroyer than a tank and was supposed to be air transportable. In few, if any, cases were they simply a cheap regular tank unlike many light tanks of the 1930s or early WW II.

 

[yulzari]

If we start off by seeing the 'light' tank as a comparative not an absolute then it must exist by virtue of being lighter than it's companions in the same army. Therefore it must fulfill a different role to them. A MBT is to engage then enemy in a firefight. A light tank can have value in only two ways. Firstly as a reconnaissance machine to use tracked mobility. Small size and light weight assist in this role. It needs only to be armed to cope with infantry or IFVs as the weight and size of an anti MBT gun would restrict it's mobility. The other role is to (poorly) substitue for MBTs either where MBT's weight and/or size preclude their use. For example on narrow mountain roads or using low strength bridges.

As for a weight, I would point to the Scimitar at @ 7 tonnes and PT76 at 14 tonnes as differing approaches that could be used as a guide. The PT76 sacrifices size to amphibious mobility and the Scimitar seeks to restrict size whilst adequate firepower. Equally the PT76 was designed to operate principally in the western USSR whilst the Scimitar was optimised for NW Europe which partially explains their differences.

Now the WW2 belligerents could not really use aluminium armour and amphibious armour would have been too bold a step to rely on. So we would be looking at a steel tank of the Scimitar class armed with something that can suppress infantry or an antitank gun so either a heavy machine gun with a good rate of fire and ammunition capacity or something that can use worthwhile HE. I would suggest that @ 50mm is the absolute minimum calibre for single shot HE and 0.5" for a heavy machine gun.

Given the weapons etc. available for WW2 belligerents to choose from an automatic 20mm cannon might be a useful compromise.

Thus I would suggest something in between the Vickers Light VI and Pz II or about T60 in size, 20mm automatic cannon, with a low ground pressure and excellent rough ground performance.

Or you could use more and cheaper (in cost, resources but necessarily life) armoured cars. I once postulated (for a certain limited budget dry but varied country) an army solely using Staghound armoured cars (suitably modified as APCs/supply vehicles, lightly armoured MBTs, A/A, ARV/engineers SPGs, for all roles. I think the principal problems were matching MBTs at range, mission kill vulnerability to mines and a large enough artillery gun (and that could be dealt with by towed artillery with the Staghound as prime mover.) I remember suggesting the limited budget air force could be best spent on good artillery, mobile A/A and light spotter/recconnaisance aircraft of the Auster/Cub class and small STOL transports of the Antonov 2 class rather than a few fighters that would last about 4 hours if they weren't destroyed on the ground: but I digress.

 

[Shortround6]

Everything is a trade off. If you want a tank to be amphibious then the hull volume must be enough to support it's weight in water (displacement). this leads to a a larger than needed or wanted hull for dry land operations. You can use detachable floats or screens but they take time to install and discard. The PT-76 could use it's guns while swimming I believe, which cannot be done with flotation screens.

Armored cars can be lighter than tanks because they don't have the the heavy track systems. As a rough guide they have half the rolling resistance of a tank and so need less power.

Heavy machine guns and even 20mm cannon have problems as the main armament for a light tank. The Heavy Machine guns generally are limited in ammo supply ( they are NOT a secondary anti-personnel weapon) and the striking power is usually insufficient for armored targets any heavier than the vehicle that mounts them.
Not all 20mm are created equal.

The Russians built over 6000 T-60 light tanks but stopped in 1942 because they really weren't very good. Too light at about 6 tons it's armor wasn't good enough against even light AT weapons. The Russian 20mm wasn't particularly high powered. It was also belt feed which made changing types of ammo not the easiest chore. Especially with the one man turret crew who had plenty of other things to do. The 70hp engine also meant it was under powered and it could not keep up with T-34s cross country which rather limited it's usefulness also.

The Russians also churned out over 8000 T-70s before realizing it wasn't the best idea either. You have a choice, send the T-70s into the middle of the battle with their one man turret, limited vision, low rate of fire and almost impossible to co-ordinate tactics/movement or stand back 500-2000yds and pound the enemy positions with SU-76s, in fact the SU-76s can fire HE to well over 10,000 yds. The Su-76 can't overrun positions but it was a much more useful vehicle.

This is the problem with light tanks, they can't carry enough armor to keep them safe OR they can't carry a gun big enough to really hurt the enemy (Matilda I) AND/OR they can't go fast enough AND/OR they can't carry a big enough crew to make the most of the weapons they do carry.

By the time the Americans came up with a satisfactory "light" tank it weighed about 20 tons (the M-24) and still didn't have very good protection. The "bow" gunner was a waste of space and weight so perhaps the tank could have been a bit smaller.

 

[psteel]

They do have to be used properly. And using them properly does not include trying to use them like or instead of tanks.

Tanks were capable of overrunning infantry positions for most of the war. It got a lot costlier with infantry hollow charge anti-tank weapons but tanks were bullet proof 360 degrees and from above. SP guns and half- tracks were not. German light armored cars were fitted with anti-grenade screens over their open turrets for a reason and even Mr Benders picture of the German Sd.Kfz.250/9 shows the anti-grenade screens.
APCs in WW II were NOT supposed to over run the target position but transport the infantry to a close distance and then support them with the vehicle mounted gun/s.

Use of the SPW was not intended to over run infantry positions, but to route infantry independantly to reach the Panzer units position and give them infantry cover.

Having said that SPW in recon units would over run/prob any enemy position it came upon as part of their recon mission. That is a vital role for light armor.

As the war progresses and mass production gets underway, this years 'tank' becomes next years 'light tank', so as much prodution as possible can remain uninterupted.

 

[davebender]

Which war are you talking about?

Light tanks such as the BT5 ruled battlefields in Spain and China during the 1930s. The same light tanks wouldn't last long vs well equipped infantry during the 1940s.

 

[Shortround6]

They wouldn't have lasted long against "well equipped infantry" in 1940 let alone later. But open topped vehicles wouldn't have lasted long against well trained but poorly equipped infantry in 1940. It doesn't take much special equipment to shoot down into an open topped vehicle, terrain permitting, let alone an open backed one. Gasoline bombs may or may not take out a tank but put one into an open topped vehicle?

That is the difference between a tank and an SP gun or open halftrack. The tank has overhead protection and even if it loses a track it can still fight 360 degrees while waiting for help.

 

[davebender]

Not all half track versions had open tops.
Not all tanks or tank destroyers had closed tops.

If you want the Sd.Kfz.250/9 or similiar vehicle to have a closed top then build it that way. Just as Czechoslovakia did when they put a top on the Sd.Kfz.251 and renamed it an OT-810.

 

[Vincenzo]

a vehicle w/o closed and armored tops is not a tank imo

 

[Shortround6]

Not all half track versions had open tops.
Not all tanks or tank destroyers had closed tops.

If you want the Sd.Kfz.250/9 or similiar vehicle to have a closed top then build it that way. Just as Czechoslovakia did when they put a top on the Sd.Kfz.251 and renamed it an OT-810.

What tank had an open top??

Some tank destroyers had open tops and some did not but tank destroyers are not tanks. SP guns on tank chassis are not tanks even if they have a 360 turret. An "AA tank" is not a real tank but a specialized SP gun.

You can close the top on an a WW II half track, that doesn't make it a tank either. Czechs also used a more powerful engine to drive their version. Armored roof is good for .2-.25 ton without hinges, supports, etc. Frontal armor of the halftracks was only good against rifle caliber bullets. Side armor was iffy against rifle caliber bullets depending on range, type of bullet and location of hit.

 

[yulzari]

I certainly agree Shortround6 that a light cannon or heavy machine gun are anti materiel weapons and a co-axial medium machine gun of the 7.7mm class is worthwhile for antipersonnel use.

 

[tomo pauk]

Prior the 1940 (under 10 tons), the armor would need to protect vs. LMG fire. The off-the shelf engine is a must, mounted along the driver so the last 2/3rds of the tank is free. The 37mm cannon was possible to fit in many tanks under 10 tons historically, the 20mm cannon should be a better choice vs. 'soft' targets*. Maybe a high-angle mounting, so the windows at higher floors can be attacked, or even the planes? A 3 man crew. After 1940, a conversion into SP artillery, AAA ond/or APC seem just natural.
German Pz-II fits the bill (apart from the powerplant layout), Brits can use Horstman suspension, there was plenty of under-100 HP engines to choose, if they can fit 2pdr - way cool. If not, maybe purchasing 25mm from the French, or 20mm Oerlikon. Besa 15mm could give the Germans Italian light competition some worries.
French can adopt 20mm HS, one of two 25mm designs (AT, AAA), or low velocity 37mm. Soviets can adopt 37mm (from the 30's ATG) + 20mm combo for production. Sweden produced some interesting designs, and the Germans have adopted the Czech light tank as the Pz-38(t).

*Italians managed to mount their 47mm on the 6500 kg vehicle, StuG-like; wonder if the turret would be able to hold it, being tailored to fit under 10t limit, total.

 

[psteel]

Well prepared infantry positions vs. armor were-at best-a mid war to late war phenomena. They rarely figured in early war clashes. Most war mechanized clashes were mobile attacks were operational considerations/decisions actions were paramount not tactical limitations of one weapon over another. In that regard, light tanks and open APC were fine, even preferable to heavier tanks. Since their consumption of supplies and maintenance was much less than heavy tanks were.

This all just sounds like tactical war gaming mentality. Tactical considerations come at the end of a very long line of other considerations.

 

[Shortround6]

37mm guns are all over the place as far as gun power goes. French actually had 2 different 37mm guns. The first used the same ammo (cartridge case) as the WW I trench gun a pretty poor armament by WW II despite being used by the thousands. There were two AP rounds for it. One was a 'HOT' load but used a light projectile. This is the 21 cal. gun the 33 cal. gun used a heavier projectile at a higher velocity and wasn't that far off the German 37mm.

The big machine guns and auto-cannon have a problem with feeds. Some Modern guns have a dual feed that can be switched from one belt to the other in 1-2 seconds allowing for both HE and AP to readily available. No such thing in WW II. Large magazines are awkward to handle in small turrets (and need a lot of turret above the gun). While the German 20mm AA guns used 20 round magazines the tank versions used 10 round magazines. They also feed from the side and not the top. The 15mm BESA gun (used in the Lt. tank MK VIC) used 25 round belts in British service and I don't believe there was an HE round for it. Even if there was, taking out a part used belt and fitting a new one would have been a difficult task inside a small turret.
The French 25mm guns (AT, AAA) used different ammo. With a projectile weigh a bit less than half a 37mm round a single shot 25mm gun does not have impressive HE capability. An automatic 25 mm gun is approaching the weight of a good 37mm gun and more importantly the breech is much bulkier which affects turret size and thus armor weight.

Dual purpose (AA) armament is not a good idea either. Tanks don't have good vision if they have a closed top and if the top is open they are not a tank. The higher elevation usually means a bigger turret or deeper hull. Rate of traverse is also none to good for an AA weapon.

 

[Shortround6]

Well prepared infantry positions vs. armor were-at best-a mid war to late war phenomena. They rarely figured in early war clashes. Most war mechanized clashes were mobile attacks were operational considerations/decisions actions were paramount not tactical limitations of one weapon over another. In that regard, light tanks and open APC were fine, even preferable to heavier tanks. Since their consumption of supplies and maintenance was much less than heavy tanks were.

This all just sounds like tactical war gaming mentality. Tactical considerations come at the end of a very long line of other considerations.

Try telling that to the German 4th Panzer Division in Poland, just for starters. Yes, they used what they had and performed on an operational level but is was part of the learning curve that taught them NOT to use unsupported tanks in built up areas. The Polish campaign also taught them that 14.5-15mm armor was not protection enough against 7.92mm Anti-tank rifles let alone heavier weapons.
APCs could get the troops closer to the battle than trucks could, air burst artillery shells at the time were time fuses and required direct observation of the target by artillery observers and good gun crews. This was NOT a new technique as Shrapnel shells in WW I were ALL airburst with time fuses. Firing on approach routes or map firing on roads, road junctions and the like without direct observation to correct the time of flight and fuse settings meant impact fuses and here is were the open APCs offered very good protection compared to trucks. Granted the APCs could cover ground faster than men on foot but then they are a bigger target too. The APCs offered a mobility that kept the infantry in reach of the tanks. By that I mean the infantry was not stuck on different road or in a different village in trucks that could not keep up with the tanks cross country.

 

[psteel]

Sounds like tactical war gaming mentality. Again the tactical considerations were ALWAYS secondary to operational considerations, which were mostly secondary to strategic requirements. The speed of the panzer assault was so swift in the first couple of years, there was little or no time to do anything other than establish a hasty defense with little depth. The Panzers and what armored infantry they had; all enveloped the opponent making such defenses' moot while artillery fixed the opponent in place. There are ALWAYS exceptions, but those should never divert the basic operational plan. Tweaking the AFVs in-between campaigns is always advisable and was done by all sides whenever possible. Doesn't mean the previous design was inferior, just that it is good enough to keep pace with developments.


Air bursting artillery was the exception, not the rule in WW-II. The vast majority of the artillery was ground burst, and certainly not in a fluid battle clouded by "fog of war". Yes in a prepared set piece determined attack this was possible but not in fluid battle situation. The situation you are describing is idealized late war allied tactics with total air superiority and information superiority, and has little bearing on the rest of the war.

 

[Shortround6]

If the tactics don't work then the operational plan won't work and then the strategic plan goes in the toilet. The Germans won in Poland but it was not the walk over some people think it was. There were very few armored "clashes" as the Poles had very little armor and much of it was even worse than the German light tanks. Hundreds of cheap light tanks or tankettes that meet pre-war "strategic requirements" failed miserably in combat and were unable to conduct operations as their owners wanted.

How many German tanks were lost or knocked out in the Polish campaign?

The "Idea" that vehicles with lighter armor and even with open tops would have done any better, even if available in somewhat greater numbers, doesn't seem to be the lesson learned.

Some countries "tweaked" such light armor right out of production between campaigns. It took a while to work through existing inventory though.

Air burst artillery was the standard for short range tactical artillery use in 1914. It may have been replaced by the machine gun but it certainly was not a new or unknown technique. While it was not used on top of friendly positions as they were being overrun it could certainly be used against the enemy before the forces mixed. Air burst in early WW II does require a trained observer with eyes on the target with what is now know as a "real time link" ie voice radio or telephone to the gun battery. Trying to use air burst on a dust cloud behind a hill or stand of trees will be ineffective and that is where the impact fuses come in ( impact fuses are also the choice against any sort of dug in target, if you are trying to damage the fortifications) Code messages take too long to de-code. Artillery use did change in all armies during the war and more in some armies than others. Improved communications between observers and batteries and between batteries and art HQTRs made for much faster response times and for more flexible concentrations. Improved communications as much to improve artillery performance as any new gun or shell.

Too heavy a tank does no good. if you can't load it on ships or get it ashore it doesn't do any good and if it can't cross a river on existing bridges or on army temporary bridges it does't do any good. However, if an army was going to mechanize and go to tanks restricting it's tanks to weight that the existing trucks and temporary bridges ( which were designed for horse drawn artillery and supply wagons or, at best, trucks) means to great a sacrifice in actual combat ability. Early tanks did have a powerful morale effect. But building tanks that cost thousands of dollars if not tens of thousands of dollars that can be taken out by AT rifles costing hundreds of dollars is not sound planning. At least build tanks that require the opponent to come up with 37-50mm AT guns that need vehicles of their own to move them. 20lb rifle vs 900lb AT gun?

 

[tomo pauk]

37mm guns are all over the place as far as gun power goes. French actually had 2 different 37mm guns. The first used the same ammo (cartridge case) as the WW I trench gun a pretty poor armament by WW II despite being used by the thousands. There were two AP rounds for it. One was a 'HOT' load but used a light projectile. This is the 21 cal. gun the 33 cal. gun used a heavier projectile at a higher velocity and wasn't that far off the German 37mm.

The big machine guns and auto-cannon have a problem with feeds. Some Modern guns have a dual feed that can be switched from one belt to the other in 1-2 seconds allowing for both HE and AP to readily available. No such thing in WW II. Large magazines are awkward to handle in small turrets (and need a lot of turret above the gun). While the German 20mm AA guns used 20 round magazines the tank versions used 10 round magazines. They also feed from the side and not the top. The 15mm BESA gun (used in the Lt. tank MK VIC) used 25 round belts in British service and I don't believe there was an HE round for it. Even if there was, taking out a part used belt and fitting a new one would have been a difficult task inside a small turret.
The French 25mm guns (AT, AAA) used different ammo. With a projectile weigh a bit less than half a 37mm round a single shot 25mm gun does not have impressive HE capability. An automatic 25 mm gun is approaching the weight of a good 37mm gun and more importantly the breech is much bulkier which affects turret size and thus armor weight.

Dual purpose (AA) armament is not a good idea either. Tanks don't have good vision if they have a closed top and if the top is open they are not a tank. The higher elevation usually means a bigger turret or deeper hull. Rate of traverse is also none to good for an AA weapon.

Okay, so for the French the 37mm L33 should be the choice? I now that the AT and AAA 25mm rounds were not the same; if they can properly shove in the AAA cannon, the HE fire is impressive, the AT properties would be better than of 20mm cannons, so the Pz-II, -38(t) and lesser tanks would be in jeopardy. Should be fine even if the elevation is only suited for the fire vs. ground targets only.
The tanks were operated perhaps 1% of the war time buttoned up. The parallelogram-operated AAA sight is a must, to replicate barrel elevation for the gun aimer that has it's head above the roof. The rate of traverse for eg. German 20mm flak was not that great either, though some foresight to design a dual purpose tank would be fine. The 20mm would be perhaps the biggest gun that fits for an under-10 ton tank.

The 20mm auto-cannon could use the magazines attached from below, so the turret top wouldn't interfere.

 

[Vincenzo]

actually japanese light tanks (~7 tons) had a 37/45 gun.

( i not mention the T-70 and its 45 because it's too near to 10 tons)

 

[Shortround6]

In a ground or Sp AA mount the gunner/s are only trying to move the weight of the gun, cradle/upper mount. In a DP tank turret they would also be trying to move all the turret armor unless you can supply power traverse. Unless you have really thin armor this is going to be a ton or more.
Some guns didn't take well to firing on their sides or upside down.

The best of the 10 ton "class" of light tanks was the Czech t-38.

With a 10 ton limit there are a number of trade-offs that have to be made. Consider the French light tanks, the Renault R-35 and the Hotchkiss R-39. Their armor was about as good as it was going to get on a light tank, 30-45mm which means that they were good against just about all AT-rifles, a fair degree of protection against weaker 37mm guns and were some what "shell proof", that is, resistant to HE shells fired by 75-80mm field guns. The nose fuses on the HE shells would either crush and fail to detonate or would detonate on contact and explode the shell with the main body of the shell not in good contact with the armor. Such hits could damage the tank, some times severely, but could not achieve the same percentage of kills that AP shot could.
The penalty for such good armor was a small size that restricted them to a two man crew. The man in the turret commanded the tank ( directed the driver) picked out targets, selected the gun (cannon or MG) loaded the cannon with appropriate ammo, aimed and fired the cannon, loaded the MG as needed, watched out for his platoon leaders signals, and so on. French tanks were rather an exception to the 1% buttoned up figure. While they were not buttoned up on the march, the commander frequently sitting on a seat formed by a fold down hatch in the rear of the turret, the tank could NOT be fought with the commanders head sticking out of the rear hatch or the cupola hatch. He would be too far away from the gun sight and the turret/ firing controls. Leaving a hatch open might give him better ventilation but it darn little for vision. BTW a similar restriction would apply to anybodies one man turret vehicles, some gave the commander a bit more vision that others.
Getting back the French tanks, they were also short and narrow. It kept the target size down and the armor thickness up but also limited their ability to be used as a chassis in other roles. Yes, they were used as gun tractors, supply vehicles and even to a limited extent as chassis for self propelled guns, but they were far from ideal because their small size meant a very limited storage capacity inside.
The German MK II offered more volume, it had a third man plus a radio set, both transmit and receive. The extra size meant thinner armor for the same weight. It also had a one man turret, latter versions got a cupola with six (?) vision blocks so the commander had a better idea of what was going on outside, but again he could not aim the guns and have his head outside the tank at the same time. Early versions gave the commander a periscope with rather limited vision. Some tanks had periscopes that turned, better in some ways but trying to maintain oreintation could be a problem. Turret is turned 30 ^ to line of travel and the periscope is turned another 30^ and try to tell the driver where to go?
Wiki has an interior shot of a Russian t-26 turret (I am on an I-PAD at the moment and cutting and pasting is a real b**ch).
The T-26 is another tank that was limited in armor protection in part due to size vs weight. 15mm armor is great a against Rifle caliber bullets and even the lighter AT tank rifle and 12.7-13mm machine gun ammo. It is NOT shell proof and is an easy mark for the lightest of real anti-tank guns. One of the criteria for the T-34 was it should have "shell proof" armor and since the HE shell doesn't really care that much about slope that should give you an indication as to what was wanted.

There is also a difference between a tank commander having his head/shoulders sticking out of a hatch ( not buttoned up) and having part of the roof missing or large gaps in the roof or turret front.

2 man turrets could come two ways. Gunner and commander/loader and commander/gunner and loader. The latter meant you needed fewer "skilled" tank men but it also meant poorer tactical co-operation between tanks or the units. Again the benefits of operating "unbuttoned" are rather diminished by the commander having to spend so much time with his head inside the turret in order to do his "second" job. T-34s could operate unbuttoned with that big hatch folded up but with the tank commander operating as the gunner it didn't really add anything to the ability of the tank.
3 man turrets are were the ability to operate unbuttoned really show up.
The Czech tank is about the only light tank to have that ability. A few British light tanks do but that is because they are armed with Machine guns and the commander is not needed every few seconds while firing to reload the gun. Of course the 12.7 Vickers can't really hurt anything heavier than a MK II either.

 

[tomo pauk]

Actually, a simple 'like' would not be enough; great post really

About the DP tank - the Flakvierling weighted 1500 kg; 'my' 2-barreled 30mm (with splinter-proof aimer position, and 100 rds) was also being capable to be aimed manually, with decent speed. Granted, a power traverse is a better thing.