Another incorrect view of the French! The French did not expect this kind of attack but they made preparations for some kind of attack that would have worked just fine if the Belgians had not run away.
The defence plan was based on the German WW1 offensive and assumed the Germans would need 7 days to make it to the Meuse and another 7 to bring enough artillery forward to attempt a crossing. So the French made sure two or three A-divisions could reinforce the sector within 5 days max. To make sure the Germans would not be able to cross the Ardennes faster they kept a QRF of several so called "Light Cavalry" divisions(4) and brigades(3) ready to support the two crack divisions the Belgians had in the Ardennes.
The problem was the Belgians did not tell the French they didn´t intend to defend the Ardennes. When the offensive began the French actually raced east, the Germans advanced west and the Belgians left northward. They barely fought but they did blow all the bridges and roads on the French side too. As a result an easy to defend area was left virtually undefended and the French QRF was swept aside.
If the Belgians had fought, well one company did and stopped the best Panzerdivision of the WH for six hours. The flank of this division would have been threatened by one division and one brigade advancing north through Luxembourg, the rest of the QRF would have literally backed up the Belgians. That puts six divisions and three brigades against 8 divisions but no more than three could advance abreast. In the lead were three armour heavy Pz.Div. and the Großdeutschland Infantry regiment.
That would have stopped the German advance. At least long enough for the reserves to reach Sedan and to loose the element of surprise. In OTL the Germans beat the reserves by a mere 12 hours.
Well said!
But still the French operational plan IMHO was much too reliant on the enemy doing what they were expected to do - that is very rarely a good idea.
And next, also IMHO, the French rather were too offensive than too defensive! They were keen on avoiding having the battleground in France like in WWI and thus fell compelled to advance into Belgium and meet the Germans there.
The French/allied strategy was about buying time until they were strong enough to undertake major offensive operations - i.e. 1941. Had Gamelin made his operational plans in accordance with the strategy he should have taken a much more cautious stance towards the German assault in May 1940 - i.e. having kept back his strategic reserve until the German main assault is definately identified - instead of committing it to an advance into Belgium - which he not only really isn't strong enough for, but which also relies on the Germans doing as expected, and if they don't, loose France the war in a few weeks - baaad plan!
So, as we are on an alternate history board, I'll claim that a PoD only changing the French operational plan into a more defensive one leaving Belgium to her own fate would be enough - same doctrines, telegrams, generals etc.
I agree on most of what has been said here about the shortcomings in the 1940 French Army, but even with these, had there been a strategic reserve to deploy in front of the German spearheads - the Germans would have bogged down before the French Army disintegrates as it did in OTL June 1940. If the French are allowed to "stiffen up" their superior firepower will decide the matter. BTW the French Army in OTL 1940 showed remarkably fast learning skills. By late May/early June 1940 they already had left the continious frontline doctrine and deployed in 360 degree (company)positions in chequerboard formation and utilising the old 75mm field guns as excellent anti-tank guns. It had the German losses accelerate, but by that time too many units already had been lost to keep the Germans back. But deploying in "hedgehog" positions in chequerboard formation became the standard way to counter massive armoured assaults in later German, Soviet and allied(NATO) doctrine.
My next claim is that the French combat morale or "will to fight" wasn't any worse than everybody else's morale. But no army's morale can survive a total chaos like that the French went into after the grand plan went wrong. That the French doctrine relied more on meticulous planning than personal initiative of course only made this worse - if the grand plan goes wrong all other plans must follow - but again morale wasn't the cause but the victim.
The myth about bad morale etc. to a large degree was created after the war by the French military establishment to take blame off their own shoulders and was quite handy in blaming the communists. Not that the communists did anything good, but their influence on the 1940 events is highly exagerated.
Regards
Steffen Redbeard