"While the tank battle was in progress, I attempted, in vain, to destroy a Char B with a captured 47-mm anti-tank gun; all the shells I fired at it simply bounced harmlessly off its thick armor. Our 37-mm and 20-mm guns were equally ineffective against this adversary. As a result, we inevitably suffered sadly heavy casualties". - - Guderian.
Guderian as describing an encounter with a French Char BI tank during the Battle of France, 1940. The Char B1 seemingly impervious to anti-tank weapons as fielded at the time.
Items of interest regarding the French Char B1 from that era of the Second World War:
1. "In direct meetings with German tanks the Char B1 usually had the better of it, sometimes spectacularly so as when on 16 May a single tank, Eure (commanded by Captain Pierre Billotte), frontally attacked and destroyed thirteen German tanks lying in ambush in Stonne, all of them Panzer IIIs and Panzer IVs, in the course of a few minutes. The tank safely returned despite being hit 140 times"
It is reputed that the Char commanded by Captain Pierre sustained one-hundred forty hits without being either destroyed or disabled. [an Internet web site forum suggest a preponderance of those hits from 20 mm cannon fire.] This somewhat reminds me of the German encounter  with a Soviet KV tank as was the topic of a previous blog entry.
DURING THE BATTLE OF FRANCE, 1940, IT IS NOT THAT THE FRENCH ARMOR, FRENCH COMBATANTS, OR FRENCH FIGHTING SPIRIT WAS LACKING OR UNABLE! THE FRENCH POSSESSED MORE ARMOR THAN THE GERMAN AND BETTER ARMOR TOO! DOCTRINE FOR EMPLOYMENT IN BATTLE SEEMS TO BE POOR.
2. "The fighting compartment had the radio set on the left and an exit hatch in the right side. All vehicles had the ER53 radio telegraphy set, which used Morse Code only."
Command and control of a Char and French armor at various echelons cannot have been easy. NO voice [AM modulation] radio communications available. Everything manual Morse and necessitating a dedicated and highly trained operator WHOSE ROLE AS A FIGHTING COMBATANT NOT DIMINISHED ONE BIT!
During that era of the Second World War the single most common reason for pilot washout during aviator training was an inability to copy manual Morse code at even the slowest of speed!