On the first of September, 1939, nearly 1.5 million troops, 2,750 tanks, and 2,300 aircraft of Adolf Hitler’s Third Reich stormed over the border into Poland. We all know what happened next: despite declaring war in solidarity, Poland’s allies Britain and France stood by and did nothing as Nazi Germany and the Soviet Union overran and occupied the country in only five weeks. What followed was a seven-month period of relative calm known as the “Phoney War”, which was finally broken in the spring of 1940 when the Germans overran Denmark, Norway, France, and the Low Countries in quick succession. Western Europe would remain under German occupation for another four years, until German defeats on the Eastern Front and the D-Day landings in Normandy finally turned the tide in favour of the Allies. But this popular narrative of the Second World War is incomplete, for often overlooked is the fact that one of Poland’s allies did, in fact, attempt to intervene early in the conflict. Barely a week after the German invasion began, 43 divisions of the French Army crossed the border into Germany in an operation that, had it succeeded, might have ended the war before it had even begun. This is the forgotten story of the Saar Offensive, one of the greatest “what ifs” in modern military history.

Modern Poland was born from the 1919 Treaty of Versailles, in which the victorious Entente powers agreed to reconstitute a Polish state from territories previously occupied by Germany, Austro-Hungary, and Russia. In the years that followed, the fledgling state fought a series of conflicts in defense of its sovereignty, including the 1920 Polish-Soviet War in which Polish forces narrowly defeated the Soviet Red Army. Recognizing the nation’s vulnerability against its neighbours, in 1921 the Polish government signed treaties with France and Britain guaranteeing that the latter would defend Poland’s sovereignty in case of foreign invasion. When, in early 1939, it became clear that an invasion of Poland was imminent, Poland’s allies debated how best to strike a preemptive blow against Germany. First Lord of the Admiralty Winston Churchill suggested floating mines down the Rhine River, but France countered that the Germans would blow up bridges across the Seine in retaliation. The idea of bombing the Black Forest to start uncontrollable fires was also proposed, but this was shot down by Secretary of State for Air Sir Kingsley Wood, who argued that this would constitute an illegal attack against private property. Instead, on May 19, Polish Minister of Military Affairs Tadeusz Kasprzycki signed a military convention with Commander-in-Chief of the French Armed Forces, General Maurice Gamelin. The convention stated that as soon as the invasion began, the French would invade Germany from the West in order to divert German forces and relieve pressure on the Polish Army.

On September 3, 1939, 2 days after the Germans launched their invasion, France and Britain declared war on Germany. French military mobilization, however, had begun considerably earlier on August 21st. Unfortunately, this process proved painfully slow. One problem was that the French mobilization system itself was woefully antiquated and inefficient, calling for the formation of small cadres of well-trained soldiers who would then train and prepare larger groups of reservists and conscripts for battle. Another problem was what would face the French troops once they crossed the border: the Westwall or Siegfried Line, the formidable line of bunkers, trenches, and other obstacles that defended Germany’s western frontier. Generals, as the saying goes, always fight the last war, and French military doctrine in 1939 was heavily mired in First World War-era thinking, with a heavy reliance on massed artillery to smash enemy defences. This was in stark contrast to German Blitzkrieg doctrine, which largely replaced heavy artillery with much more mobile ground attack aircraft like the infamous Junkers Ju-87 Stuka. It thus took time for the French to pull these heavy artillery pieces out of storage and move them into position along the border, further slowing the mobilization process.

Nonetheless, by the time of the German invasion, the French Army had successfully mobilized 40 regular infantry divisions, three mechanized divisions, one armoured division, 40 tank battalions, and 78 artillery regiments under the command of General Gamelin. These were to be further reinforced by 4 infantry divisions of the British Expeditionary Force and the advanced striking force of the Royal Air Force, which began landing in France on September 4. On paper, this gave the French an overwhelming numerical advantage over the Germans. With most of its armed forces tied up in Poland, Germany had only 43 highly-depleted infantry divisions with which to defend its entire western frontier – a massive front stretching from Denmark to Switzerland. The Saar Region, where the French planned to attack, was defended by only 34 divisions under the command of General Erwin von Witzleben – all but 11 of which were composed of poorly-trained reservists mainly armed with WWI-era weapons. Making matters worse, von Witzleben had only recently been recalled from retirement, and had only a few hundred armoured vehicles at his disposal – mostly lightly-armed Panzer I and II training tanks. The French, by contrast, fielded one of the best tanks of the period: the Char B, equipped with powerful 47 and 75mm guns and thick armour the German 37mm antitank guns could not penetrate.

On September 7, 1939, four days after France’s declaration of war, eleven French divisions of the Second Army Group under the command of General André Prételat crossed the German border along a 32-kilometre front near the town of Saarbrücken. As expected, resistance was almost nonexistent, and in a single day the French advanced 8 kilometres and captured 12 towns with few losses. By September 9, when heavy and mechanized infantry divisions crossed over the border, the French occupied most of the Warndt Forest and had advanced within a few kilometres of the Siegfried Line. The atmosphere as the French advanced was strangely calm – and in many cases surreal. In several towns French troops encountered hand-painted signs declaring “French soldiers, we have no quarrel with you. We shall not fire unless you do,” or propaganda loudspeaker vans blaring pro-French messages. In many towns, mills and factories continued to operate, while along the border German and French customs agents chatted casually to each other as if nothing had happened. Indeed, in most areas the French assault was so leisurely in places that German officials were able to pack up their belongings and retreat ahead of the advancing troops.

Yet despite this promising start, the French assault soon ground to a halt, in part due to the infantryman’s worst enemy: land mines. The fields and forests of the Saar were heavily sown with various anti-tank and anti-personnel mines, including the dreaded S-mine or “bouncing Betty” – which we previously covered in our video The Terrifyingly Effective Nazi De-Bollocker. In one town, French troops succeeded in clearing a minefield by driving a herd of pigs through it, though one can imagine that the resulting carnage did little to improve the soldiers’ morale. Another problem plaguing the French Army was its poor use of its armoured divisions. While the French had excellent tanks, unlike the Germans they had no cohesive operational doctrine for using them. Thus, instead of supporting the infantry’s advance, French tanks were used in showy but redundant assaults on German frontier defences while French government VIPs watched from behind the border. And those tanks that did penetrate into Germany quickly discovered that they were of little use, for even without the Siegfried Line, the hilly and heavily-forested terrain of the Saar was extremely difficult for vehicles to negotiate. This was completely intentional, the border between France and Germany having been drawn in the wake of the Napoleonic Wars to provide a natural barrier against future French invasions. Worse still, the French quickly discovered that their otherwise excellent Char B tanks had a fatal weakness: their engine radiators were mounted on the side of the hull, allowing them to be easily disabled by small-arms fire. The heavy artillery around which the French had based their attack also proved inadequate, for a shortage of delay fuses meant that shells could not penetrate bunkers and pillboxes before detonating, making them all but useless against the Siegfried Line.

But the French Army’s greatest disadvantage was not material or tactical, but psychological. France had suffered greatly during the Great War, losing nearly an entire generation of fighting-age men. This deep national trauma, as well as two decades of political turmoil and stagnation, had left the French Armed Forces poorly organized and highly demoralized, with little appetite for another major conflict. This lack of fighting spirit was evidenced by an incident in which a single machine gun defending a German village held up the French advance for an entire day.

All this gave German forces time to regroup and reorganize, and on September 10 a German counterattack retook the village of Apach. However, French forces managed to reverse this loss only two hours later, and on September 12 captured the town of Brenschelbach for the loss of only nine men. But the Germans were swiftly gaining strength, and on that same day the Anglo-French Supreme War Council gathered in Abbeville, France, and decided to hold offensive actions immediately. General Gamelin ordered his troops to hold their ground and not advance closer than 1 kilometre from the Siegfried Line. Shockingly, the Poles were not informed of this decision; instead, they were merely told that the planned full-scale assault was being postponed from September 17 to the 20th. Then, on September 21, Gamelin ordered a complete withdrawal of French troops from German territory. Several French commanders, including General Henri Giraud of the 7th Army, decried the order, arguing that Gamelin was throwing away a massive opportunity. Giraud believed he could capture and consolidate the area between Saarbrücken and Trier, giving France control over the strategically important Kaiserlautern Gap and allowing for future assaults into western Germany. However, Gamelin ignored Giraud’s protests and the withdrawal carried on as ordered.

The French withdrawal was nearly as slow and disorganized as the initial advance, such that most of the invading French forces were still in the Saar on October 6, the day Polish resistance finally collapsed. The surrender freed up thousands of German troops and hundreds of aircraft, who were immediately redeployed to the west to counter the French. Almost immediately the French Air Force began suffering heavy losses against better-equipped and more experienced Luftwaffe pilots, leaving the troops vulnerable to aerial attack. Then, on October 16, German troops under General von Witzleben launched a major counteroffensive against the French. Though the French were already in full retreat, they fought a valiant rearguard action and inflicted heavy losses on the Germans. But by the next day the withdrawal was complete, with all French troops having returned to their starting positions behind the French border. The Saar offensive had been a complete failure, with the French suffering nearly 2,000 killed or wounded against only 200 casualties on the German side.

Several German commanders, however, saw the offensive as a close-run thing. At the Nuremberg war crimes trials in 1946, Commander of the Army Generaloberst Alfred Jodl stated:

“If we did not collapse already in the year 1939 that was due only to the fact that during the Polish campaign, the approximately 110 French and British divisions in the West were held completely inactive against the 23 German divisions.”

Similarly, General Siegfried Westphal stated that had the French had pressed home their attack in force, they could have reached the Rhine within two weeks, forcing Germany to sue for peace.

Such statements inspired the popular notion that the French foolishly threw away a golden opportunity to end the Second World War early, dooming the world to six years of the most destructive conflict in modern history. Contemporary historians, however, dismiss this claim, arguing that the Saar Offensive never stood a chance. Though thinly manned at the time of the invasion, the Siegfried Line was still a formidable barrier against which French artillery was all but useless, and would have held up the French advance long enough for the German defenders to reorganize and counterattack in force. There was also the matter of air superiority. Even with 90% of its strength tied up in Poland, the Luftwaffe’s aircraft and pilots greatly outmatched those of the French Air Force, allowing them to strike at French troops with impunity. And even if the French managed to break through the Siegfried Line and reach the Rhine, their lack of rapid assault doctrine would likely have prevented them from capturing any bridges before they were blown by the Germans, leaving the invasion stranded on the river’s western bank. All this would have allowed the Germans to hold off the French for long enough to finish conquering Poland, releasing the troops necessary to beat back the invasion.

Thus, while the story of the Saar Offensive makes for an intriguing historical “what if”, the plain truth is that the French in 1939 were woefully ill-prepared for modern mechanized warfare – a fact that would become horrifically clear when, only 8 months later, the Germans came storming across the border and conquered France in only six weeks.