I doubt that the armour on an R35 is face hardened. It is most likely mild steel which was the usual early on.
The R35 used cast armor for both the hull and the turret. I don't think any nation produced cast armor with face hardening. Face hardening was only done on flat rolled plates.
That does not mean that the R35 was "mild steel". That would be a ridiculous assertion. It was armor grade steel.
And contrary to the implication, face hardening was not a technique that became common in later tanks. Rather, it was a limited-use development. It was only feasible with flat rolled plate, and only economical for relatively thin armor. It's advantages were easily overcome with blunt-faced penetrators with ballistic wind caps. Because of these factors later German tanks all had homogeneous rolled flat plates, not face-hardened.
The R35's armor was probably in the range of 210-240 BHN. (I do not have stats on R35 armor hardness, but U.S. Ordnance cast armor plate, as used on M4 turret production throughout the war, was about 220 BHN. Thinner plate, as on the R35, could well have been a bit harder.) German rolled homogeneous armor, as used on late war Panthers and Pz IVs, was about 260 BHN, while thinner rolled homogeneous plates used on the turret or hull sides of the Pz III and many of the 8-wheeled armored cars were about 360 BHN. German face-hardened armor plate, as used on the hull front on the later marks of the Pz III (mid-war 1941-43 production) was about 585 BHN on the face, with 365 BHN backing.
Most of the french tanks were pretty tough by 1940 standards.
Their weakness lay in 1 man turret, low velocity 37mm gun, and gas guzzling engines which did not allow opportunities to exploit a breakthrough cause they have to stop and refuel.
Spot on!
Imagine the job of the commander in an R35 tank. There is no turret-roof hatch to peer out of (the only way to be "heads up" is to open the turret rear/side panel, a full 1/6th of the turret wall, and sit with 2/3rds of his body out of the tank!). He must scan for targets, instruct his driver, and coordinate with his platoon and company. When he does spot a target he must take his eyes out of the sites to find the appropriate ammunition, then load the gun, then go back to the scope to re-acquire the target, aim and fire. Then observe the fall of shot so he can correct his next shot, then take his eyes out of the sites again, find the right ammo, load the gun again, go back to the sites again, find the target again, correct his aim, and fire again. And if his platoon commander puts up a flag indicating advance or withdraw or whatever, well good luck noticing that in any reasonable length of time!
So … French tanks tended to drive to positions, then sit. If the Germans came, they shot at them. If not, they sat. Eventually the commander might decide to go somewhere else to sit. He would walk from tank to tank describing the new plan, and then they would roll out together. If they found themselves in combat while on a road march, they would mostly stop, sit, and fire. There was very little maneuvering during combat.
Best method is to divide and conquer overwhelming each tank with multiple tanks and ATG hits hoping to demoralize them into retreat. Concentrate on flanks and rear. Or use very brave infantry trying to untrack them.
While I have never seen hard stats, from the first hand accounts it seems that French tanks often received many hits for each shot they took. Sometimes many dozens of hits.
When a tank is hit, it often takes some damage even if not penetrated. Interior spalling and reduction in effectiveness of various mechanisms (drive wheels, turret traverse, ventilators, etc.) may all occur. Yes some crews managed to stay in the fight after 100 or more hits. But not many …
But for the Germans, the best method for defeating the French tanks was simply to go around them. A panzer formation could drive right through the French armor, merrily shooting as it went, and continue on its way. French tanks needed to refuel every 2 hours or so. So the supply echelon was never far behind. There was no path by which French tanks could catch up with Germans running around in their rear areas. Once the supply echelons were destroyed or disbursed, the tanks were nothing more than speed bumps for the engineers to clear away.
The same was observed in Russia in 1941.
The same was observed by U.S. forces running across France, and Russians rolling over Byelorussia and Poland, in 1944. If your armor is more mobile than your opponents, once you have the initiative you will find a large portions of your opponent's force abandoned along road as you advance.
-Mark
(aka: Mk 1)
