When the war did begin, the French made a token advance (less than 10 miles) and then immediately withdrew behind the Maginot Line despite having a 2-1 advantage in troops (much of the French force was reservists, but almost ALL of the Reich's forces were also reservists, and much more poorly equipped reservists at that), a 40-1 advantage in towed/mobile artillery and better than a 20-1 advantage in armor (with French tanks being of higher quality, although with much worse fuel economy). The Reich had almost literally nothing in the West, virtually the entire Luftwaffe, all panzer divisions, and nearly all front line infantry formations were engaged in Poland. The French could have been in Frankfurt, if not Munich, before the Heer could have redeployed. The French civilian AND military leadership were utterly unwilling to act offensively until the British were fully deployed. They missed the chance to END the War by October 1st (The Heer did not manage to launch a reasonable counterattack until October 17th, and it was in anything but strength.
tl;dr: Talk is cheap.