By Dale Cozort
The G1 was a French project to produce a new tank in the late 1930s. In 1935 specifications were issued for a twenty tonne medium infantry tank and in 1936 French industry was invited to offer potential designs. Seven companies would submit plans in 1937. The French already had a reasonably good tank for the role in the Somua S-35, and Somua proposed a revised version of the S-35 in the competition, but the infantry wanted their own design and there were some legitimate issues in using the S-35 in the role, given its high unit price and poor mechanical reliability, though the type could probably have been revised to meet infantry requirements if the will had been there.
Regardless, given war would not break out until 1939, there was probably time to get a tank from the G1 competition into production. Moreover French industry was genuinely enthusiastic about building a tank in that category, with most of the historic French tank producers sending proposals and a few outside companies like SEAM trying to get in on the action. The problem was that the specifications kept changing, leaving the companies trying to design the tanks playing a never-ending game of catchup.
The biggest changes were to the main gun and armor thickness. The original specs called for a 47-millimeter gun like the one on the S-35, but that got switched to a 47 mm gun, plus a 75mm gun in the front hull just as most of the companies involved in the competition got ready to build their prototypes. That made a kind of sense at the time, using a high-velocity 47 mm gun against tanks and a low-velocity 75 mm gun with better high-explosive shells against infantry. That was the same trade-off that the Germans made, only they divided the functions between two separate tanks, with the Panzer III having a smaller but relatively high velocity gun and the Panzer IV a short-barreled, low-velocity 75 mm gun.
The Germans eventually combined the functions, putting a high velocity 75mm gun in the Panzer IV. The French also realized that they could combine the functions, and changed the specs again, now requiring a 75 mm gun in a turret. That was certainly an improvement, but it meant that companies had to go back and rework their plans, and any prototypes and other work they had done were obsolete. Armor thickness went up too. Thicker armor and a bigger main gun pushed the projected weight up to well over thirty tons, probably to around thirty-five tons. The added weight meant engines and suspensions had to be revised. After a few years of trying to chase the ever-changing specification, several companies dropped out, while others gave the project lower priority.
A few companies stayed in the competition, with Renault producing one wooden mockup that would have met the updated specs before France fell. SEAM produced one actual prototype aimed at the original spec, a nice-looking tank, based on the few surviving pictures. That was the extent of the program's accomplishments. The Renault version might have, in a couple years, evolved into a decent tank, if the specifications didn't keep changing. In terms of gun and armor it would have been comparable to a Sherman or a T34, though it probably wouldn't have had the mobility of those tanks and Renault tanks of this era were notorious for wearing out ridiculously quickly.
Oddly, a French light tank project, the AMX-38, grew until it met the original G1 specifications and reached the prototype stage, with the second prototype being the closest the French came to a new medium tank for the infantry.
Ironically, the French already had a tank that on paper met the specifications, the D2, but it was so poorly built that it wore out after a ridiculously short time in the field. Despite the issues, the French ordered 50 more D2s with a new high-velocity 47 mm gun to sort of fill the gap when it became apparent that tanks weren't coming out of the G1 program any time soon.
Implications: The French infantry was trying to develop their own version of an armored division, the DCR. It was visualized as a heavy club of an affair, as opposed to the rapier of the German panzer divisions. The DCR would throw overwhelming firepower and armor at a section of the front lines, crushing the enemy there and hopefully allowing the more mobile cavalry-based armored divisions (DLMs) to exploit the breakthrough.
Would that have worked? Probably not, but it never really got a chance. Without a viable medium tank, the French infantry built their armored divisions around the B1 heavy tank. The B1 was potentially not an awful tank, but it had the same weird setup that was briefly required for the G1, with a 47mm gun in a turret for anti-tank work and a 75mm gun in a fixed mount in the hull for anti-infantry uses. The two main guns meant that it required a highly trained crew. The B1 was also very complex to build because using the fixed 75mm gun meant slewing the whole tank around, which required an expensive and finicky transmission. With an aggressive commander and a well-trained crew, the B1 could be formidable as one crew proved by a rampage that knocked out ten German tanks with their single tank, but aggressive commanders and well-trained crews were a rarity.
By the time war broke out, the French had enough B1s to outfit one brigade. They made a huge industrial effort involving most of the French tank companies and managed to produce enough B1s to outfit 3 DCRS by May 1940. They managed to toss one more DCR together during the Battle of France, though it had a non-standard order of battle, basically the tanks the French had available tossed together, including a considerable number of the S35 cavalry tanks the infantry had rejected early in the G1 competition. Unfortunately, most of the divisions were recently activated, without enough time to develop unit cohesion or a good sense of how to use their tanks. The first two DCRs were formed in January 1940, while the third DCR was formed in March 1940 and had never held any exercises as a division, or even above the company level before they were thrown into battle in May 1940. Their commander felt (rightly or wrongly) that they were incapable of working as a division. As a result, he used them as mobile pillboxes in penny packets around the battlefield at a point where an armored division acting as a division could have tossed the Germans back at a key bridgehead.
Let's say the infantry gets their medium tank, the one in the initial spec. Maybe they freeze that spec, choose a tank based on the prototypes, produce it and start a separate project for a future infantry tank. They build their DCRs around the new tank, with the relatively simple design produced in large enough numbers that three divisions are available before September 1939 and have time to work up before the actual battle. Maybe the (fewer) B1s produced are allocated a certain number per armored division, if they can keep up with the rest of the division, or more likely put in one or more heavy tank brigades. The French probably have another couple DCRs forming by May 1940 too.
Is all that enough to change the course of the battle? I don't know. The French doctrine envisioned a type of battle that was dramatically different than the one the Germans forced on them and they designed tanks based on that vision. Especially for infantry tanks, the French insisted on enough armor on their tanks that they were close to invulnerable to German antitank guns, but their suspensions tended to be so overloaded by the extra armor that they broke down after a ridiculously few miles in the field and the thick armor pushed them toward very cramped interiors that made actually fighting from French tanks very difficult. The one-man turrets were the most obvious manifestation of that problem, but the interior layout overall made the tanks difficult to fight from, with poor vision and a lot of other problems. French tanks were also notoriously difficult to repair in the field, including the S35.
German control of the air made any French defence difficult, as did the millions of refugees that clogged French roads and French dependence on telephones and messengers rather than radios for command and control. French doctrine also emphasized methodical battle, with hastily organized offensives frowned on. Also, the French pushed their best forces way too deep into Belgium, committing much of their mobile reserve on the assumption that the Germans would push through Northern Belgium rather than the Ardennes into southern Belgium. The Germans pitted the best of the German army against the worst of the French army, reserve divisions operating in a poorly located economy of force operation.
Despite all that, there were a few times when a functioning French armored division in the right place, especially one with tanks meeting the original G1 spec, could have stopped the Germans, so maybe this would have mattered.