DURING the course of 1918 the alliance between the Entente powers and the United States grew in cohesion, at sea as well as on land, and in its control of global resources and its capacity to use them for the purposes of the war. At the same time, tensions between the Central Powers, Germany, Austria-Hungary, Bulgaria and the Ottoman Empire, intensified. One alliance rallied, and the other fell apart. The consequences determined both how and when the war was won.

Outwardly, for the first six months of the year, Germany looked to be both strong and getting stronger. By the summer its writ ran from central France to Ukraine, and from the Baltic to the Balkans. Under the terms imposed on Russia at Brest Litovsk in March and on Romania at Bucharest in May, it had established a dominance over European Russia which promised the resources that would enable it to sustain the war for a little longer. Contained in this victory, however, were the seeds of the German-led coalition’s dissolution.

Success in the east created competition, between Germany and Austria-Hungary for food from Ukraine and between Germany and the Ottoman Empire for the oil of the Caucasus. In September, while struggling to hold their lines in the west, the Germans developed grandiose plans for the east which clashed with those of the Ottomans as the Turks sought compensation for their loss of Arabia and their defeats in Syria and Palestine. None of Germany’s allies had any interest in the war in France and Flanders: their ambitions lay closer to home. Their peoples were hungry and tired of war.

With their territorial ambitions satisfied by the conquests of Serbia and Poland, and the defeats of Russia and Romania, they had no reason to carry on fighting. Their inclination was to seek peace, not to help their arrogant ally fulfil its western ambitions.

On September 15, a multi-national Entente army attacked in Macedonia. Its commander, Franchet d’Esperey, a hero of the first battle of the Marne, had told the French president in late 1914 that manoeuvre was possible in the Balkans and he now backed his words with deeds. Bulgaria asked Ludendorff for reinforcements but it did not get them. In the past the Germans had countered such crises by shuttling troops across Europe from one front to another. Now they were running out of men and they struggled to move them. Their railways were suffering from over-extension and inadequate maintenance. Within two weeks, on September 29, the Bulgarians sought an armistice.

The effect on Ludendorff was immediate. He and his superior, Paul von Hindenburg, had been so focused on the Western Front that they had ignored the dangers looming elsewhere. Ludendorff feared that the allies would breach the Central Powers from the south in short order despite the poor state of the roads and the imminence of winter. Franchet d’Esperey imagined himself entering Vienna in triumph, the first French general to do so since Napoleon in 1809. Ludendorff said that it was the collapse of Bulgaria in the Balkans that prompted him to seek an immediate armistice in the west.

Although he exaggerated the imminence of the threat to Germany itself, Ludendorff was right about the implications for what he called the Quadruple Alliance. The allied breakthrough in the Balkans would cut Germany’s communications with the Ottoman Empire. As Franchet d’Esperey’s armies advanced on the Danube, the British component turned eastwards through Thrace towards Istanbul. On September 19, Edmund Allenby had inflicted a major defeat on the Turks in Palestine at Megiddo. Although this victory too would not deliver its full effects until 1919, the Ottoman government realised that it needed to seek terms. The Turks signed an armistice with the British at Mudros, on the island of Lemnos, on October 30.

The Austro-Hungarians followed suit. They had long described the Germans as “secret enemies” and the young Habsburg emperor, Karl, who had succeeded Franz Josef at the end of 1916, had been anxious both to distance himself from Berlin and to seek a way out of the war. His army fought with skill and determination on the Italian front but its last offensive, on the Piave in June, failed and, when the Italians attacked at Vittorio Veneto on October 24, they achieved a quick success. The Austrian armistice was signed at Villa Giusti on November 3.

This was a full month after the German request for an armistice had been despatched to the American President, Woodrow Wilson. Wilson informed his allies of Germany’s position, which was public knowledge by October 8. So, although the Turks and Austrians reached their own decisions independently, the Germans could hardly claim they had been betrayed. The German army was later to claim that it had not been defeated in the field but had been “stabbed in the back” by collapse at home. This too inverted the sequence of events.

At the end of September, German soldiers were still fighting well inside France. At home their families were – like all the peoples of belligerent Europe – exhausted and war weary.

A succession of poor harvests combined with the blockade to cause hunger and promote social disintegration. The entry of the US into the war had eased the principal constraint on the allied economic war – the need to respect neutral rights – and the economies of the states abutting Germany suffered as severely as those of any belligerent.

But Ludendorff was wrong to distinguish Germany’s army from Germany itself: citizen soldiers were influenced by, and themselves shaped, the mood at home. The revolution that broke out in Germany in early November, sparked by mutinies in the navy, followed the request for an armistice, rather than preceded it. The Kaiser abdicated on November 9 but he did so because Ludendorff’s successor as First Quartermaster General, Wilhelm Groener, had told him that he had lost the confidence of the army, not because he had forfeited that of his subjects.

Throughout October, the allies were uncertain whether or not the Germans were serious in their request for an armistice. Philippe Petain wanted the French army to free Lorraine by force of arms in 1919 and John J Pershing felt the American Expeditionary Force had just started fighting. He hoped it would capture Metz. Douglas Haig was the more cautious of the allied commanders, partly because he underestimated the renewed strength of the French army and the potential of the American army, but also because he argued that the German army was not yet defeated. He recognised, too, that the pace of the allied advance would slow as their lines of communication lengthened and winter set in. Why, he asked, if the Germans were ready for peace, lose more lives and for what? Haig helped ensure that the war ended sooner than the politicians expected or some of his fellow commanders wanted.

The corollary of Haig’s position was that the armistice terms had to do duty for the absence of a “decisive” victory to match the precedent of Waterloo in 1815 or even of Megiddo or Vittorio Veneto in 1918 itself. The result was that all the armistices had to perform two functions, and that with Germany especially so. First, the enemy was required to surrender so much equipment – in the German case 5,000 artillery pieces, 25,000 machine guns, and 5,000 locomotives – that he would not be able to resume fighting: this was the substitute for the destruction of the enemy army on the battlefield. The degree to which the allies had continued to over-estimate Germany’s residual strength was shown in some cases by their demanding more than it could deliver. On Britain’s insistence, Germany also surrendered the bulk of the High Seas Fleet and 160 submarines.

Secondly, the armistices were technically only temporary pauses in the fighting. They were therefore designed to ensure that the allies secured the capacity for strategic manoeuvre in the event of hostilities resuming. The Turks had to open the Dardanelles and permit the allies use of the Black Sea; the Austrians had to allow the allies to advance into Bavaria; and the Germans had to give up the Rhine bridgeheads, so opening the east bank to the allied armies.

Some feared these conditions might be too harsh to be acceptable and others that the fall of the Kaiser would mean that there would be no German government authorised to agree them. The German delegation, headed by Matthias Erzberger of the Catholic Centre Party, was brought through the lines in secrecy to a location in the forest of Compiegne, where its presence could not be observed. No German general accompanied it, although both Ferdinand Foch, as allied generalissimo, and Sir Rosslyn Wemyss, the British First Sea Lord, represented the allies. For the victors, this was a purely military arrangement, despite its political consequences. The Germans agreed the terms at 5.10 am (backdated to 5.00 am) on November 11. The armistice was to take effect at 11am the same day.

Sir Hew Strachan is Professor of International Relations at the University of St Andrews and a member of the WW100 Scotland Panel.

Tomorrow in the Herald on Sunday: Hew Strachan on the war that was easier to start than to end.