Thursday, January 25, 2024

Military Geography of Operation Sickle Cut


Germany’s invasion of France in May and June of 1940 could cross the border at three locations: the Maginot Line, the Ardennes Forest, and the Plain of Flanders. The French considered the Maginot Line to be secure. They believed that Ardennes was impassible by German Panzers, and so they defended it with minimal forces. French General Maurice Gamelin thus designed his Dyle-Breda Plan to defend Flanders by amassing troops along the Franco-Belgian border.

Germany instead believed that Ardennes was a viable invasion route and so amassed Army Group A at the least-defended part of the border: the Ardennes Forest, while placing the smaller Army Group B at the Belgian border. This was the starting arrangement of the German forces according to General Erich von Manstein’s Case Yellow, also called Unternehmen Sichelschnitt – Operation Sickle Cut.

French and German War Plans at the Start of the Battle of France
From Galgano (2009)

Germany indeed attacked through Belgium, and the Allies responded by sending their forces into Flanders to repel Army Group B. Germany’s incursion into Belgium was feigning maneuver, however.

Almost simultaneously, Army Group A with its seven Panzer divisions entered the Ardennes Forest on 10 May, crossing it in only three days. Once on French soil, the Germans turned north and reached the English Channel by 21 May. This encircled the Allied forces at Flanders, trapping them against the English Channel. This also separated the Allied forces at Flanders from those assigned to defend central France, including Paris. A little over a month later, almost half of France was occupied, and the armistice and cease fire between France and Germany went into effect on 25 June.

Geographic Analysis: Physical Component

Galgano (2009) argues convincingly that the Ardennes Forest was the most pivotal geographic element at the start of the Battle of France. The Ardennes, with its dense forest, rugged hills, and deep gorges, made the forest difficult to cross, restricting travel mostly to roads running along river valleys. There is one part of Ardennes, however, through which heavy armor could pass: the Losheim Gap (Winters, Galloway & Reynolds, 2001, p. 49). The Germans used this gap at the start of the sickle cut, sending seven Panzer divisions into France on 10 May 1940.

A physical component that played a role at the end of the sickle cut is the English Channel, which worked as a barrier against which the Germans pinned the French, British, and Belgian forces. Besides forcing the Allies to evacuate their troops, the English Channel also served as the German's right flank as they continued their march westward through France.

Geographic Analysis: Cultural Component

The most important cultural component was the French General Staff’s attitude that the Ardennes was impossible to cross using heavy armor. The analysis of prior commanders lent credence to this: the WWI French General Charles Lanrezac is quoted as saying that "if you go into that deathtrap of the Ardennes, you will never come out" (Winters, Galloway & Reynolds, 2001, p. 48), and Marshal Pétain in 1934 called the Ardennes "impenetrable," but amended this by stating that "if any enemy attacked he would be pincered as he left the forest. This is not a dangerous sector," adding "as long as we make special provisions" (Jackson, 2004, p. 32) - those provisions presumably being support from the Belgian Army as well as the use of French troops trained at slowing or halting an advancing force. This latter option was viable, for "the terrain also decentralized offensive command and control while favoring small-unit defensive operations" (Winters, Galloway & Reynolds, 2001, p. 49).

The belief that the Ardennes was impenetrable by heavy armor had solidified before the start of WWII, as the French halted construction of the most fortified part of the Maginot Line south of Ardennes (Galgano, 2009). Even the French 1938 summer exercises in which a notional German force defeated French forces in Ardennes (Galgano, 2009) was not enough to challenge this dogma, as General Gamelin attributed this loss to a lack of adequate reserves. Galgano (2009) attributed Gamelin’s self-delusion to “an unconscionable sense of intellectual lethargy.”

The assumption that Ardennes was impassible was held by French commanders right up to the start of the Battle of France. Even when it was clear that Germany would attempt an invasion, the French side of the Ardennes Forest was guarded by a force used in an inappropriate manner by the commanders who placed them there, which Galgano (2009) dismisses as "second-rate" and the "worst divisions in the French Army." Further, the French apparently did not perform reconnaissance (either aerial or even basic ground patrols) to monitor activity on the German side of the Forest.


Would these military geographic components still be considered important today? The physical components that made the Ardennes difficult to penetrate are still there (except maybe for deforestation and modernized roadways), but physical impediments are made less important due to improvements in heavy armor technology and the ability to deliver such armor through means other than over-land. The English Channel is still of value for its ports and the proximity of the Lille industrial district. To any enemy of France, those ports and the Lille district continue to be assets worth controlling. The fact that the English Channel is a body of water will forever constrain the movement of ground forces. (Galgano & Palka, 2010, pp. 50)

It is not clear whether the cultural components would still be in place: WWI ended more than a century ago, and the military commanders that saw the Battles of Flanders (and desired not to see it repeated) are long gone, as were the commander who wanted to refight the previous war. The institutional dogma about the impenetrability of the Ardennes Forest by heavy armor may still be in place as a form of command inertia, either ignoring the history and geography of the Battle for France or by ignoring basic infantry skills in favor of "high tech" approaches to area denial.


Galgano, F. A. (2009). " Sichelschnitt ": A geographical analysis of a decisive campaign, France, May 1940. In P. Nathanail, B. Abrahart and R. Bradshaw (Eds.), The History and Technology of Military Geology and Geography, Nottingham, United Kingdom: Total Graphics, Ltd.

Galgano, F. & Palka, E.J. (2010). (Eds.). Modern military geography (1st ed.). Routledge.

Jackson, J. (2004). The fall of France: The Nazi invasion of 1940. OUP Oxford.

Winters, H.A., Galloway, G.A., & Reynolds, W.J. (2001). Battling the elements: Weather and terrain in the conduct of war. John Hopkins University Press.

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