Other generals would be shaken by the losses in Lorraine, but Joffre is unflappable. He knows the Germans are pouring troops into Belgium and he knows they have deployed many troops in Alsace and Lorraine. Surmising that they cannot be strong everywhere, he sends his troops to attack the German centre, ordering them to advance into the Ardennes and to Luxembourg. But the Germans are stronger than Joffre thinks. They have deployed far more of their forces in the West than he thinks. Also, they have sent reserve formations to the front straight away rather than keeping them in the rear.
When French troops advance on the German centre, they are met by strong forces intent on staging an offensive of their own. Both sides suffered terrible casualties, but the French take the worst of it, suffering 27,000 killed in one day’s fighting. This will be the worst carnage of the entire war and it sees the French offensive brought to a bloody halt almost as soon as it has begun.
image source (Wikipedia)