Blitzkrieg 1940

(from the rulebook:)

Blitzkrieg 1940 is a two-player simulation of the decisive first three weeks of the campaign fought across the Low Countries and northeastern France during May of that year. The Allied player, primarily on the defensive, controls French, British, Belgian and Dutch forces, and is opposed by the invading German player, who commands units of that nation's army, air force, and SS.

There is also an alternative history 1939 scenario covering the possibility of a French offensive toward the Ruhr a few days after the war began.