Key point: These tanks were nigh impenetrable, but they couldn't save France.

At five o’clock in the morning on May 16, 1940 a company of the 8th Panzer Regiment lay in an ambush position along a rubble-strewn street of the French town of Stonne. The day before, the unfortunate village had changed hands several times as French troops attempted to stem the tide of German armor headed toward the English channel, threatening to trap Allied forces in Belgium.

Three squadrons of Stuka dive bombers ravaged Stonne, as well as both French and German artillery. That morning, the Panzer IIIEs and IVDs—then the best tanks in German service—deployed to stave off a French counterattack.

Suddenly, a squat green tank lumbered around a street block directly before of the German unit. This was Eure, a 31.5-ton Char B1 bis tank commanded by Capt. Pierre Billotte. His driver, Sergeant Durupt, triggered the 75-millimeter howitzer fixed in the front hull roared, smashing the Panzer III to the rear of the column. At the same time, Billotte swiveled the smaller 47-millimeter high velocity cannon in the turret and picked off the lead tank—a mere 30 meters away.

The wrecks trapped the Panzer company in a head-to-head confrontation with the Gaelic behemoth. 37-millimeter rounds cracked from the long barrels of Panzer III tanks and ricocheted off Eure’s turret. Low-velocity 75-millimeter shells made basso thuds as they spat out the stubby guns of Panzer IV tanks, only to shatter in clouds of shrapnel against the French tank’s glacis.

More than 140 shells cratered Eure’s armor—but none penetrated. Billotte coolly blasted one Panzer after another.

Once he had destroyed the entire company—11 Panzer IIIs and two Panzer IVs in all—Billotte continued his advance and added two 37-millimeter anti-tank guns to the tally. By 7:00 A.M., Stonne was back under French control and would remain so for the rest of the day. The same day, the tank Riquewhir would charge into a column of enemy infantry, its blood-stained tracks causing the German 64th Schutzen Regiment to panic and flee an entire sector of Stonne.

For the first time, the Wehrmacht had encountered a tank that completely that outmatched its own.

France will of course go down in history for being defeated by tanks in World War II, but it was not due to lacking tanks—the French army fielded nearly 4,000 tanks of more than a dozen different types, most of them well-armored. Rather, poor organization, confused doctrine and disastrous operational conduct defeated the French military.

The Char B1 was conceived only a few years after World War I as an infantry support tank with a heavy assault role. The “battle tank” would tackle enemy fortifications, artillery and tanks head-on, prevailing through superior firepower and armor. The slow heavies would punch holes allowing faster “cavalry tanks” to penetrate behind enemy lines.

The resulting design revealed its World War I-era pedigree with huge tracks as tall as the hull intended to ford trenches with ease—as well as its multiple cannon armament. A heavy 75-millimeter howitzer was fixed with only vertical traverse in the hull for blasting pillboxes. It was operated by the driver via a sophisticated Naeder hydraulic system for precise aiming, and serviced by a loader. Additionally, a small turret on top mounted a 47-millimeter gun for hunting tanks. There were also machine guns in the turret and hull for close defense against infantry.

It took nearly a decade and a half before the first B1 was ready to enter production in 1937. A short initial run of 35 Char B1s was quickly superseded by the B1 bis model, with higher-velocity SA35 47-millimeter gun for busting enemy tanks and a 300-horsepower engine. Most notably, the B1 bis boasted 55 to 60 millimeters of armor on all sides, leaving it virtually without major weak points. For comparison, the Panzer III and IV had only 20 to 35 millimeters of armor.

Despite completely overmatching its peers in firepower and armor, the B1 had major flaws. It could only achieve a maximum speed of 17 miles per hour while contemporaries typically averaged 25 miles per hour. The B1’s range of 110 miles wasn’t actually worse than that of German medium tanks, but it required tons more fuel. The French army even experimented with having the B1s tow extra fuel supplies in a trailer, then decided to rely on fuel trucks, which were vulnerable and in short supply.

The B1 also suffered from the one-man turret endemic to French tanks. A B1’s commander had to give verbal commands to his crew and possibly the other tanks in his unit, aim and fire the 47-millimeter gun in the turret and reload the gun. It was simply too much do efficiently. Even though the turret gun could theoretically fire up to 15 rounds a minute, a rate of fire of four rounds per minutes was more typical.

A final weakness of the Char B1 was its rudimentary ER53 radio, through which the operator could only transmit simple commands via Morse code! Even though an audio receiving model later became available, it was considered inferior because it was drowned out by the roar of the engine. By contrast, German Panzers all had excellent radio communications, affording commanders much finer tactical and operational control.

At least 369 B1 Bis were manufactured by Renault and four additional French companies. Each was individually named after a French city, colony or even wine. They were not cheap — 1.5 million francs each, four or five times the cost of a light tank. Three B1 ter prototypes were also constructed with five-man crews, 70-millimeters armor plates and 350-horsepower engines, but the Third Republic fell before they could enter production.

France entered World War II with only four battle tank battalions, or BCCs, each with 33 B1 tanks. By the time major ground operations began in May 1940, two BCCs each served in three reserve armored divisions, or  DCRs, that were intended to support the infantry. A fourth DCR was hastily formed under command of Gen. De Gaulle, as well as five independent companies for supporting infantry formations.

Unfortunately, the DCRs were gravely lacking in logistical and repair services, a weakness compounded fatally by the Char B1’s high fuel consumption and frequent breakdowns. As air strikes and armored columns caused the French logistical system to collapse, more Char B1s were abandoned for lack of fuel or necessary repairs than were destroyed in combat. The DCRs’ infantry regiments also lacked motorized transport to keep up with the tanks. Invariably, the B1s roamed ahead into battle without infantry support.

Nonetheless, the B1s were very tough—flat-out invulnerable to the 20-milimeter gun on the Wehrmacht’s most numerous tank, the Panzer II. Panzer III, 38t and IV tanks only had a slim chance of penetrating at ranges under 100 meters. All were easily destroyed by both of the B1’s cannons.

Only 88-millimeter flak guns could reliably take out a B1. For example, Jeanne d’Arc continued running despite being struck by 90 shells and losing both of her main guns, before finally being dispatched by a flak gun.

The French tanks occasionally were disabled by smaller guns. In the first day of the battle for Stonne, a Panzer IV knocked out the B1s Gaillac and Hautvillier, while an anti-tank gun destroyed Chinon with a hit aimed at the side armor. Billotte’s unit, the 3rd DCR, was eventually deployed elsewhere, and Stonne fell to German forces on May 19 after changing hands 17 times.

However, a concurrent French counterattack in Flavion, Belgium better illustrates how the near-impenetrable armor, superior firepower and bravery and determination of the French tankers could not makeup for failures in logistics and combined-arms coordination.

On May 15, the 62 Char B1s and 80 H39 light tanks of the 1st DCR rolled forward to block the advance of more than 546 tanks of the 5th and 7th Panzer Divisions, the latter commanded by Erwin Rommel. The lopsided numbers were typical of the German superiority at concentrating their armored forces to decisive effect.

The B1s deployed to battle at 8:00 A.M. short on fuel, many of their supply trucks already lost due to air attacks. Just 26 tanks of the 28th BCC rolled forward to block the 7th’s path. Four had already broken down. From atop a hill, they began picking off swarming Panzer IV and 38t tanks. The German armor charged, closing within 100 meters, only to be scourged by 47- and 75-millimeter shells. Sousse took out seven tanks, Phillipeville six and other tanks averaging three each. In return, only a single B1 was knocked out and another damaged. The Panzers retreated.

Rommel then committed a Panzer regiment to a flanking attack which was countered by a company of B1s—some of which ran out of fuel in the process, forcing them to manually rotate their turrets. Three immobilized B1s were swarmed by a dozen German tanks each, their armor scoured by small-caliber shells until the crews were forced to bail. But the German probe turned back.