An operational/strategic simulation of the Western Front between June and September, 1944, the game simulates the invasion by the Allies of France while it was occupied by the Axis Powers. The title references the Normandy Landings in France on 6 June 1944, but it is actually about the campaign to liberate France in World War II, while the invasion itself is a fairly perfunctory affair completed on the first turn.
One unique aspect of the game offers the Allied player the choice of where to invade. Players may (and often do) choose the Normandy beach where the actual invasion took place, but are free to invade at several other alternate locations, including the southern coast of France. The German player has considerable freedom as to where to place his starting pieces, but they do so without knowledge of where the Allied player will invade.
Although other games with much more complexity and realism have since been released, including Avalon Hill's early 1980s Fortress Europa covering roughly the same scale and subject matter, D-Day is still played in part due to its simplicity. Along with Stalingrad and Afrika Korps, it was considered one of the "classic" games released in the 1960s by Avalon Hill, all of which shared a similar move-attack-advance game system.