France’s first WWII attack was a massive Nazi trap

Germany lacked many of the natural resources necessary to make war in the 20th Century and knew that it had to rack up victories and seize materiel early in World War II to be successful, and that's why it was so great for its forces when France made its first offensive of World War II — exactly according to German plans.

France and Germany both knew that World War II was in the cards even as the ink was wet on the treaties ending World War I. Some French leaders openly balked at the terms of the treaty, feeling that they gave Germany too much financial clout to eventually rebuild its military, and German leaders headed home knowing that the peace terms would be unpopular, potentially leading to a revolution.

So, France prepared for a mostly defensive war against Germany, constructing the Maginot Line and securing an alliance with Belgium for mutual defense. In Germany, meanwhile, there were years of heartache followed by a surge in support of leaders who claimed that World War I was lost by politicians, not soldiers. Once Hitler became chancellor, and other pro-war groups made headway, Germany began re-arming as well.

The seeds of World War II had germinated, and everyone tried to get their ducks in a row for the coming fight.

For France, the plan was to send second-rate troops to the strong line of fortresses known as the Maginot Line while first-rate troops in tanks and other modern weapons would head north and east into Belgium to help the Belgians hold the line along rivers, canals, and Belgian fortresses.

There was one gap between the Belgian lines and the Maginot Line: The Ardennes Forest, a thick, heavily forested and hilly area that was thought too thick and treacherous for most tanks.

Germany's plan, meanwhile, was predicated upon the French one. Germany knew that the Maginot Line was nearly impenetrable and attacks against it would be suicidal. They also knew that Belgium, a historically neutral country with a young king, was a relatively weak ally. But, best of all for Germany, they knew that their tanks could get through the Ardennes, but it would be slow and challenging.

On France's Ardennes assumption: It wasn't quite as crazy as it sounds. Tanks had only been around for about 20 years during the final ramp up to World War II, and most World War I tanks had been useless on steep slopes, truly uneven terrain, and even thick mud.

The idea that tanks could make it across the muddy, uneven ground in the thick forest and hit French positions might have seemed insane.

But America's Christie tanks were much more mobile than their predecessors, and the company that manufactured them sold designs and patents to Russian firms after the U.S. Army declined to order them. The Russian tanks had served opposite German forces in the Spanish Civil War in 1936. It was clear that engineers could come up with rough terrain designs, and Germany had even got some good looks at successful designs just in time for World War II. Britain tried to warn France of the dangers in the Ardennes gap, but France barely listened.

And so Germany set a trap. First, German forces began breaking tenets of the Treaty of Versailles, including invading and occupying the Sudetenland, an area of Czechoslovakia populated primarily by ethnic Germans. France and England, not yet ready for war, signed the Munich Pact that allowed Germany to hold the Sudetenland if they just promised super hard not to invade anyone else.

Belgium's King Leopold II, worried that his treaties with France and Britain were worthless, re-declared Belgium's neutrality and re-organized the military for purely defensive purposes.

For France, this was a huge problem. Now, instead of holding joint drills with Belgium and having permission to stage troops in Belgian territory for co-defense, France could only deploy into Belgium after Germany invaded. That would set off a race between France and Germany to take strategic territory quickly if war broke out.

And France was so preoccupied with this race that, when Germany invaded the Low Countries in May, 1940, France sprinted 39 divisions across Belgium. Meanwhile, Germany parked an army group near the Maginot Line to keep France from pulling troops from there.

This meant the Ardennes was guarded only by trees, and Hitler was jubilant. His tanks were tied up in traffic jams throughout the forest, a few good tank battalions or some skilled bombers could've stopped the push through the Ardennes cold. Instead, German armored forces were unopposed as France focused its attention north.

The entire Army Group A, with seven armored divisions and another 37 of other types, spilled into Belgium and France well to the rear of where France expected to face any opposition. While French forces fought valiantly across Belgium, they were preoccupied with the massive force that maneuvered its way to Paris.

France had fallen into Germany's trap, marching their forces into the Belgian plains while Germany's jaws closed around Paris. On May 14, 1940, just weeks after Germany invaded, French forces withdrew from Paris to save the city from the fighting. French forces began attacking their own oil and weapon stockpiles to limit what Germany would take in victory.