The Balkan Wars, whose centenary falls in 2012 and 2013, shaped the geography of modern Europe almost as much as the two world wars, banishing Turkey to the sidelines of the continent. Unlike the two world wars, however, the Balkan Wars’ effects were sudden and catastrophic. At the beginning of 1911 the Ottoman Empire was still one of the largest states in the Balkans, stretching as it had for hundreds of years from Istanbul to the shores of the Adriatic and including many of the greatest cities of southeastern Europe.

Just two years later, by the spring of 1913, Turkey had lost its European empire for ever and was fighting desperately to defend Istanbul, with the capital’s fate dependent on the Çatalca Line, a string of 30 forts from Terkos, on the Black Sea, right down to Büyükçekmece, on the Sea of Marmara, today a suburb of Istanbul. A further defeat might have meant the end of Turkey.

But how did this come about – and why so suddenly? The first big blow to Turkish power in the Balkans had come in 1878, when the empire lost about two-thirds of its territory at the Congress of Berlin. The newly created Christian successor states to the Ottomans (Greece, Serbia and Bulgaria) were all eager to grow further at Ottoman expense, but even during the empire’s weakest years they were not strong enough to go to war with it. Worse still, their claims to land to liberate overlapped and conflicted, and there were two further still-submerged nationalities, the Albanians and Macedonians, also eager for their homelands. The region’s flashpoint was Macedonia, where a violent three-way struggle had been in progress between Greeks, Bulgarians and Muslims for over a decade. This had already triggered one enormous upheaval: the July 1908 uprising inside the Ottoman Army which turned into the Young Turk revolution, which in turn ended 32 years of personal rule by Sultan Abdülhamid.

Immediately after the revolution a British diplomatic despatch compared Turkish and Bulgarian military strength and concluded that the Bulgarians were stronger. Aware of the empire’s weakness, successive Ottoman governments worked to remodel it along modern administrative lines, with the army restructured on German lines under a chief of general staff.

But before the modernisation was complete, Turkey suffered an unexpected hammer blow. In September 1911 Italy invaded her outlying provinces in Libya, taking Tripoli in just a fortnight. Turkish resistance regrouped and scored some tangible successes, but in retaliation an Italian fleet sailed into the Aegean, grabbed the almost entirely undefended Dodecanese and temporarily blocked the Dardanelles.

So in the summer of 1912 Turkey was reeling from a humiliating defeat. Its political life, now based on a parliamentary system, with the sultan a mere figurehead, was in constant turmoil. As governments tried to grapple with the empire’s problems, tempers were feverish. Old-guard politicians strove to retrieve the situation, while the military became ever more entangled in politics and administration. The most powerful group of junior officers, though as yet excluded from power, was the Committee of Union and Progress, the Young Turks’ party and secret society which had made the 1908 revolution. It was largely disregarded by the empire’s veteran politicians.

There were changes of government in July and in October, but the strong man in both cabinets was Nazım Pasha, the 56-year-old minister of war. A tough veteran soldier, trained by the French at the Saint-Cyr military academy, Nazım was on very bad terms with the Committee of Union and Progress but powerful enough to impose his terms on the cabinet.

As summer advanced, Montenegro launched mountain raids against Turkey’s Albanian provinces, trying to seize Shkodër (then Scutari). Serbia, Bulgaria and Greece were also becoming bellicose. The Turkish government spent the summer and autumn trying to stave off hostilities through diplomatic approaches to the Great Powers. The Great Powers were unwilling to become involved, and certainly not as peacemakers, which would have prolonged Turkish rule. Both Austria and Russia had long-term ambitions over the Balkans and Istanbul, but neither yet felt ready for a war against the other.

To keep the Italians out of the war, Turkey negotiated a humiliating peace with Italy, purchasing neutrality by surrendering Libya and the islands while many officers plausibly believed they stood a fair chance of winning if they continued to fight. But the peace was not signed until mid-October, at almost exactly the moment that war officially broke out with Serbia, Bulgaria and Greece.

Public opinion and the mood of the army were wildly excited and strongly in favour of a war to teach the Balkan countries a lesson. This was the time when Turkish nationalism was forged, as seen throughout the 20th century, with mass meetings in Istanbul.

While Turkey was struggling to make peace, its three Balkan enemies, who normally distrusted each other, had struck a pact to fight together. What was the catalyst that enabled them to do so? Perhaps it was Russia, which certainly exerted a subtle backstage influence in nudging the rival countries to form an alliance against the Turks. But the Times correspondent in the Balkans, James David Bourchier, an Irishman and firm friend of the Bulgarians and Greeks, and a long-standing opponent of Turkish rule, also seems to have played a part. Straying far outside the supposed neutrality of journalism and representing nobody but himself, Bourchier used his good offices with the kings and prime ministers of the Balkans to persuade three chronically suspicious countries to swallow their differences and form the alliance known as the Balkan League. The result was that in late October 1912 the armies of Bulgaria, Serbia and Greece co-ordinated their attacks: something the Turks did not expect.

The size of the war area and the military balance between the two sides helps explain why the alliance was needed, and also why it succeeded. Turkey was estimated to have a total of 500,000 men and 1,000 artillery guns in Europe, while its most formidable enemy, Bulgaria, had only 400,000 men and 700 guns. Altogether, contemporaries estimated, the Balkan League could put about 700,000 men in the field, but was better equipped, with a total of 1,550 guns. On the other hand, Nazım Pasha, now declared supreme commander, and his deputy, Hadi Pasha, had to plan strategy and tactics for several war theatres. Turkey had two big war theatres to defend and several minor ones, and was fighting in a vast arc from the Adriatic to the Black Sea.

The main priority for the Turkish commanders was to defend Thrace against Bulgaria. Bulgaria had the best army and was known to be aiming at the former Ottoman capital of Edirne and Thrace. Edirne was a major military stronghold.

If it fell, the rest of Thrace and Istanbul would be in acute danger. So the eastern front received the most attention and resources. However, it was there that things turned out worst of all.

Nazım Pasha’s plan was to use Edirne as bait, defending Turkey’s border with Bulgaria only lightly and luring the main Bulgarian army into Ottoman territory, where they would be encircled by two corps coming from the north and south. That would knock out Bulgaria and safeguard Istanbul, and the alliance would be shattered.

War was not declared until October 17, after Turkey rejected a Balkan League note demanding concessions in Macedonia. The Great Powers issued warning notes to both sides but made it clear they would not interfere in the struggle. Troops of the Balkan countries then massed. Nazım Pasha made a dignified and chivalrous proclamation, which impressed Europe. King Ferdinand of Bulgaria issued a bragging crusader manifesto, talking of the war of the Cross against the Crescent and saying he was continuing the work of the Russian tsars. Europe was less impressed; the fieyhülislam, the empire’s foremost cleric, responded with a declaration of Holy War. Muslim populations in the Balkans were terrified and began fleeing to Turkey for safety.

In the next three days the Serbs captured Prishtina and Novi Pazar, and a few days later routed the western Ottoman army at Kumanova, capturing Skopje (Üsküp) on October 26. The Ottoman high command had completely underestimated Serbian military capabilities and paid for it with a rout which ended five centuries of rule.

Simultaneously there was an even bigger disaster in Thrace. The Bulgarians had not fallen into Nazım Pasha’s trap but advanced on Kırklareli (then Kırk Kilise), capturing it on October 24 and then Rodosto (Tekirdağ) six days later, defeating the Turkish army in a massive battle lasting several days at Lüleburgaz. Consequently Edirne was cut off and under siege, while the Ottoman forces fled back to the Çatalca Line on the outskirts of Istanbul. Turkish prospects now looked very poor. “It is no longer an army, it is a collection of pitiful creatures who are incapable of self-defence… against the irresistible attack of the Bulgarians,” wrote the Times correspondent.

On November 4 – two-and-a-half weeks after the declaration of war – the Ottoman government, realising the position was hopeless, appealed to the Great Powers to help achieve a ceasefire. But the Powers did not reply. So an Ottoman Greek deputy, Musurus Bey, was sent to put out feelers for a bilateral deal with Bulgaria.

But the Balkan League armies pressed ahead on all fronts. The two great prizes were Salonica (Thessaloniki) and Edirne, and questions were already being asked in the world’s press about the future of Istanbul – where the bombardment along the Çatalca Line could be heard for weeks. Salonica fell quickly. Serbia, Bulgaria and Greece all sent armies. Taking the island of Thassos on the way, the Greeks seized Salonica and appointed a Greek governor on November 8. (The former Sultan Abdülhamid II, who was in exile there, had been whisked to safety four days earlier on a German gunboat.) Taking Salonica was the crowning achievement of the 50-year reign of George I of Greece – though only two months later he would be murdered there by one of his countrymen.

Edirne proved more stubborn. The city withstood a combined Bulgarian and Serbian siege for nearly four months before surrendering on March 29, 1913. The capture was seen as the greatest feat of Bulgarian arms and a major step towards taking Istanbul. As it turned out, the Bulgarians would be in the city for less than four months themselves, and they had taken it only with help from the Serbians.

The empire’s entire future now depended on holding the Çatalca Line, and at first the Bulgarians and their friends in Europe were optimistic of their chances of taking it. In mid-November the German press even reported that the line had been pierced. The report was wrong. The Powers again made it clear they were not prepared to help Turkey. In a speech at the Guildhall on the day Salonica fell, Herbert Asquith, Britain’s prime minister, pledged that the victors would be “allowed to keep the prizes of victory”.

What did these words mean in human terms? As Asquith spoke, the fields and roads of Thrace were full of refugees fleeing from the lost territories. It was not only Turks but also Greeks who fled before the Bulgarian arms; Muslims across the Balkans bore the brunt of the defeat. The Times reported: “Over 30,000 [Muslim] families are believed to have entered the capital during the last three weeks.” The full figures for this forced migration – ignored at the time and hardly noticed since – are horrendous. Around 450,000 refugees arrived in Turkey and were settled across Anatolia, but the number of dead may have been more than three times that. This was the price paid for creating a predominantly Christian Balkans, where Muslims would afterwards survive only in isolated pools.

Throughout the rest of the winter and into the first months of 1913 the fighting dragged on, but the line at Çatalca held. The Great Powers presented a note to Turkey offering peace terms which would have ceded Edirne. The old guard, Kamil Pasha, the grand vizier, and Nazım Pasha, felt there was no alternative but to give in. The Ottoman cabinet was at work in the vizier’s offices drafting its acceptance on January 23 when Talat Bey, one of the committee’s three main leaders, appeared with a demand from the Young Turks for Kamil Pasha to resign. It was brushed aside. Just after lunch the cabinet became aware of a crowd of 200 people in the street outside, waving flags and led by Enver Bey, the most charismatic of the Young Turks, on a white horse. Enver and Talat stormed into the cabinet room and, at gunpoint, forced Kamil Pasha to write out his resignation, which was promptly conveyed to a dismayed sultan.

Kamil’s readiness to resign was no doubt increased by an incident as the Young Turks forced their way in. Nazım Pasha, bristling with indignation, had confronted the intruders and been shot dead on the spot, doubtless considered a fitting end for the man who had lost the entire European Ottoman Empire outside Istanbul.

The old guard was swept aside and for the first time the Young Turks held power directly, with a veteran general, Mahmut fievket Pafla, heading a cabinet in which Enver was minister of war and Talat minister of the interior. The Young Turks pledged to turn the tide of the war and save Edirne for Turkey. By July they had done so. The later stages of the First Balkan War, however, are a story for another occasion.