Everywhere, civilians gathered in town squares to celebrate, young men anticipated adventures of derring-do and chivalry. ‘It’ll all be over by Christmas’, the British army was told; ‘You’ll be home before the leaves fall’, declared the Kaiser to his troops. For the Russian Tsar, Nicholas II, a victorious war would stifle the murmurings of revolution that was infecting his kingdom. For France, still chafing over its defeat in the Franco–Prussian War in 1871, war offered a chance to re-establish its reputation.

Unlike her European counterparts, Britain had no standing army, only a small professional force, the British Expeditionary Force (BEF), numbering a mere 100,000 men (compared, for example, to Germany’s 1.1 million). It was this tiny army that arrived in northern France to bolster the French effort. The Kaiser dismissed the BEF as a ‘contemptible little army’, hence British soldiers took pride in calling themselves the ‘Old Contemptibles’.

The first major confrontation between the Great Powers took place in the Belgium town of Mons on 23 August; Britain’s first battle on mainland Europe since Waterloo almost a century before. The ‘contemptible’ BEF, despite being outnumbered three to one, inflicted huge casualties on the Germans, delayed their advance, and then retreated in good order. The Retreat from Mons was, as legend would have it, guided by the ‘Angels of Mons’, ghostly apparitions who safely led the British soldiers away from the battlefield.

The Germans advanced through France but were rapidly running out of steam, too exhausted to maintain the momentum. By early September they had reached the River Marne, only thirty miles north of Paris. The military commander of Paris, General Joseph Gallieni, was old enough to remember 1871 when the Prussians, Germany’s predecessors, had besieged the capital to the point of starvation. He had no intention of allowing the Germans anywhere near Paris again.

After three days of fighting at the Marne, the Germans looked poised to break through the French and British forces, and onto Paris. Gallieni was to send reinforcements but while he had the troops he had no means to transport them north. In a flash of ingenuity, he seized every available Parisian taxi – 600 of them – crammed each one full of soldiers and sent them on their way to meet the army of the French commander-in-chief, General Joseph Joffre.

The arrival of Gallieni’s taxis saved the day. It was on the River Marne that the Schlieffen Plan came to a shuddering halt. Paris was safe and now it was the turn of the Germans to retreat. They fell back, forty miles north, to the River Aisne where they stopped and dug in. The Allies tried to dislodge the Germans from their defensive positions but, failing to do so, began to dig their own trenches.

General Joffre moved part of his force northwards of the Aisne to try and outflank the Germans. The Germans, now led by Erich von Falkenhayn, moved a comparable number of men to block Joffre’s manoeuvre. Joffre repeated his tactic – as did the Germans, each side constructing trenches as it went along. It developed in what became known as the ‘Race to the Sea’ as each army tried to out lap the other until they both hit the Channel. A similar charade extended the line of trenches south from the Aisne to the Swiss border.

The war of movement had come to an end. The consolidation of defence had triumphed over attack. Stretching 400 miles from the English Channel to Switzerland, lay a network of trenches. They were to remain, by and large, in place for four long years. As 1914 drew to a close, the idea of a short, sharp war had all but vanished. Offence was no match against deeply entrenched defence. Generals on all sides puzzled over this uncomfortable truth.

On Christmas Day, 1914, British troops in the front-line trenches could hear the Germans singing Stille Nacht (Silent Night). The British joined in. Cautiously, soldiers on both sides climbed out of their trenches and walked towards each other across No Man’s Land. They shook hands, exchanged cigarettes, and took photographs of each other.