What about Antwerpen in F 14?

[FM WarB]

It seems to me that the German goal is the defeat of the french army, not the Belgian army. If Antwerp is merely masked, how far would a Belgian sortie have to go to do any real damage? How much would be on the tip of the Belgian spear, and how much would have to remain in Antwerp and on the LOC.?

Arriving German reinforcements and activating reserve forces are plenty to deal with a Belgian sortie. Joffre would be chortling if two full German Corps (+) were removed from the attack on his left flank.