One hundred years ago last week, the First World War’s outcome hung in the balance. Had the Battle of the Marne gone a little differently, the war might have been over before the first Canadian volunteer left for Europe.

In early September 1914, six German armies totalling well over 600,000 men stood on French soil. They stretched in a broad arc from the Swiss border, westward via Verdun to the gates of fortified Paris. France’s civilian government had fled. The Germans were on both sides of the Marne River.

The Germans intended to swing wide through neutral Belgium, to envelope Paris and the French armies. The idea was to crush France before Russia could attack Germany from the east. In five weeks of marching – up to 400 kilometres – and fighting through sweltering heat and dust, often ahead of their supplies, they pushed the French and the small British Expeditionary Force (BEF) before them.

Initially, the French attempted to stick to their own plan. But their charges of tightly packed troops were pulverized by artillery before even reaching the enemy. The French 75 mm field guns were famously fast and accurate, but German artillery was more numerous, heavier and generally better applied.

The slaughter in this “war of manoeuvre” was almost unimaginable by today’s standards. In August, the French suffered over 200,000 casualties (killed, wounded and missing), the Germans, perhaps half that. On August 22 alone, 27,000 French soldiers were killed. Ironically, the bayonet – which strikes fear into normal humans and was seen by some generals as their weapon of choice – accounted for only 0.25% of the war’s casualties.

Despite the volumes written about the Marne, Canadian historian Holger Herwig wrote a groundbreaking book on the battle five years ago titled, The Marne, 1914. Delving for the first time into formerly inaccessible East German archives, he wrote mainly from the standpoint of the attacker – but it was no apologia.

To Herwig, the German general staff was mesmerized by the idea of envelopment, hoping to annihilate the French as Hannibal slaughtered the Romans at Cannae. Yet, despite a flexible command structure, the tactics employed by German corps and army commanders could not achieve it. Had it been done right, it could, over the five weeks, have reduced the French and prepared them for defeat.

Joseph Joffre, chief of the French general staff, had also been obsessed with offensives. Now he proved a genius of orderly retreat, opportunistic repositioning, plugging holes, thickening stretched lines, bringing up reserves – all while eyeing the terrain and the state of the Germans for the moment to counterattack. As the Germans advanced, the French left flank was repeatedly exposed, but the German’s never “turned” it. They missed multiple chances to surround large French formations. Pursuing this phantom led the German right wing to follow the French retreat east of Paris.

Related: France recalls centennial of ‘Taxis of the Marne,’ desperate operation to save Paris in the First World War

The commanders of the two sides virtually reversed their national stereotypes. Herwig describes Joffre as tirelessly shuttling among his army commanders, using modern technology, sacking those who failed him, making the most of aerial reconnaissance and battlefield intelligence, gaining first-hand knowledge and emitting a string of informed decisions. Hounding the French railways, Joffre transferred whole army corps from his failed offensives in the east to counter the Germans before Paris. By early September, he had assembled a new army (unknown to the Germans) around the capital, first purely for defence, but then to strike at the Germans.

His counterpart, Helmuth von Moltke, was hardly the paragon of ruthless Prussian military efficiency. He just sat in his Luxemburg headquarters, attempting to run the war with a single wireless telegraph, without telephone lines to the two “strike” armies. Moltke hardly even commanded this “Imperial” army. Two of the seven army commanders on the western front were crown princes, including the Kaiser’s son; another was a grand duke; two others were former war ministers of Saxony and Prussia. So diplomacy in handling these towering, yet insecure, egos was paramount. Nerves frayed, what we today call “meltdowns” were frequent. Moltke’s vague suggestions were delivered by messenger and typically arrived a day late to armies continuously on the move.

On Sept. 6, Joffre and his British allies – over a million strong – attacked all along the line. Joffre was attempting his own envelopment, hoping to annihilate the German First Army on the Marne southeast of Paris, and perhaps the Second Army, as well. Events clearly repudiated the Hegelian/Marxist view of the “inevitable course of history”: individuals matter, and they decided the Marne battle.

The First Army’s Alexander von Kluck was the best the Germans had. Despite his scant use of aerial reconnaissance, he recognized Joffre’s threat to his right flank just in time. Force-marching troops to the northwest, he broke the French attack. But the Second Army to his left had pulled back under French pressure, opening a 50 kilometre gap. The BEF was ambling – literally – up the middle.

Several German commanders were terrified, including Moltke; rendered barely functional by the pressure. His response: to send a mid-level functionary to check things out. Herwig richly describes Colonel Richard Hentsch visiting the army commanders in turn. He reached the Second Army late on Sept. 8, commanded by the sclerotic, 68-year-old Karl von Bülow. Bülow maintained his Army had been “reduced to cinders.” Stunned, Hentsch proposed that the Second Army withdraw.

This meant the Germans would end their entire concept of operations, cashiering any hope of defeating the French and go on the defensive. A world-changing decision, made by two unnerved men in a field headquarters. The next morning, on a dusty road in Mareuilsur-Ourcq, Hentsch stunned Kluck with the demand he withdraw, as well. Kluck had, after all, planned to win. Herwig asserts that Kluck should have ignored orders and attacked.

So the final die was cast. The unbeaten First Army withdrew, ending the Battle of the Marne. Bülow had three “crying fits,” Moltke suffered a nervous breakdown and was dismissed. Joffre was, through it all, unflappable. The BEF’s commanders still ambled – largely protecting their men from the slaughter.

Had the Germans beaten the French, or the Allies enveloped the German First and Second Armies, it might still not have ended the war. The Germans might have traded land for peace, but the Kaiser wouldn’t offer it and his opponents weren’t listening either.

With two months fighting resulting in 500,000 casualties in the West alone – before any trench warfare – it’s outrageous that neither side tried to end the war then and there. Ultimately, the decision on the Marne was a negative one, in that it prevented the war from ending early, dooming millions, including over 60,000 Canadians.

– John Weissenberger is a Calgary geologist. George Koch is a freelance journalist and entrepreneur. All four of their grandfathers saw combat in the First World War.