Battle Map - AlliedvsGermanPlansMay1940

Contrary to popular perception the Allies chose a defensive
deployment scheme that actually was fairly aggressive. Given the
Maginot line's defensive strength and the unfavorable terrain lining the
Franco-German border; the allies believed a German offensive needed
to come through northern Belgium. The Allies believed that on the
Belgian plains the British Expeditionary Force (BEF) and French
motorized armies could meet and defeat the German army. The Allied
Commander in Chief, French General Maurice Gamelin based his
strategy on using the combined strength provided by Belgian
defensive fortifications supported with French reinforcements, most
notably in artillery, at the Dyle River. In early 1940 Gamelin modified
the Allied defensive plan to take into account a German attack
including the Netherlands. Gamelin's plan sought to carry the fight as
far to the east as possible. The Allied defensive plan however labored
under the burden brought by two problems. First, the Allies
presupposed German planners regarded the heavily wooded and hilly
Ardennes in southern Belgium as impenetrable. Therefore, the Allied
command assigned inadequate forces to the Ardennes for even
defensive blocking efforts. The second problem underlying allied
defensive plans related to the first problem. Allied defensive plans
were predicated on Belgian defensive fortifications buying enough time
for the advancing Allied armies to arrive at the front. All in all, it was
not a bad plan; it just had the misfortune of facing a better plan; one
more successfully married to a tradition for waging war perfectly
designed for a Western European application.

General Erich von Manstein's plan, having replaced the unoriginal and
unimaginative OKH plan for defeating France, coupled simplicity with
deception and concentrated strength. It featured strong German
armies attacking into the Netherlands, drawing allied forces to meet
what appeared as the German army's main attack axis. At the same
time the primary strike force, including the strongest armored
concentrations, attacked through the thinly defended Ardennes and
penetrated deep behind the Allied forces advancing into Northern
Belgium and the Netherlands. Upon breaking out of the Ardennes the
German armor would turn northwest, driving to the English Channel,
and trapping the Belgian army, Dutch army, the BEF, and France's
best armies in one huge pocket. Thus, Manstein's plan met the
essential elements underlying German army doctrine since Prussian
successes in the 19th Century; in seeking a decisive blow.

Map Courtesy of: Department of History, United States Military
Academy