Macedonian front

A propaganda postcard commemorating the victory of the Central Powers over Serbia in 1915.

The retreat of the Serbian troops in the winter 1915/16 across a snowy mountain in Albania to Adriatic coast.

A dead Serbian soldier in the snow.

Exhausted Serbian soldiers on the seashore in the expectation of Allied ships, February 1916.

After the victory of the Serbian army in the Battle of Kolubara in December 1914, the Serbian front saw a lull until the early autumn of 1915. Under the command of Field Marshal August von Mackensen, the Austro-Hungarian Balkan Army, the German 11th Army and river flotillas on the Danube and the Sava began an offensive on 6 October 1915, the largest offensive against Serbia. By September 1915, despite the extreme sacrifice of the Serbian army, the Austro-Hungarian Balkan Army, having crossed the rivers Sava and Drina and the German 11th Army after crossing the Danube, occupied Belgrade, Smederevo, Požarevac and Golubac, creating a wide bridgehead south of the Sava and Danube rivers, and forcing Serbian forces to withdraw to southern Serbia.[12]

On 15 October 1915, two Bulgarian armies attacked, over-running Serbian units, penetrating into the valley of the South Morava river near Vranje up to 22 October 1915. The Bulgarian forces occupied Kumanovo, Štip, and Skopje, and prevented the withdrawal of the Serbian army to the Greek border and Thessaloniki (Salonika).[13]

For a year, the Allies (Britain and France) had repeatedly promised to send serious military forces to Serbia, while nothing had materialised. But with Bulgaria's mobilisation to its south, the situation for Serbia became desperate. The developments finally forced the French and the British to decide upon sending a small expedition force of two divisions from Gallipoli (fr:156e division d'infanterie[14] and 10th (Irish) Division respectively) to combine into an Army of the Orient under the French commander Maurice Sarraill, to help Serbia, but even these arrived too late in the Greek port of Thessaloniki (Salonica) to have any impact in the operations. The main reason for the delay was the lack of available Allied forces due to the critical situation in the Western Front. The Entente used Greek neutrality as an excuse, although they could have used the Albanian coast for a rapid deployment of reinforcements and equipment during the first 14 months of the war. (As the Serbian Marshal Putnik had suggested, the Montenegrin army gave adequate cover to the Albanian coast from the north — at a safe distance from any Bulgarian advance in the south in the event of a Bulgarian intervention.) The Entente also delayed due to protracted secret negotiations aiming at bringing Bulgaria into the Allied camp, which event would have alleviated Serbia's need for Franco-British help.[15]

In the event the lack of Allied support sealed the fate of the Serbian Army. Against Serbia the Central Powers marshalled the Bulgarian Army, a German Army, and an Austro-Hungarian Army, all under the command of Field Marshal Mackensen. The Germans and Austro-Hungarians began their attack on 7 October with a massive artillery barrage, followed by attacks across the rivers. Then, on 11 October, the Bulgarian Army attacked from two directions, one from the north of Bulgaria towards Niš, the other from the south towards Skopje (see map). The Bulgarian Army rapidly broke through the weaker Serbian forces which tried to block its advance. With the Bulgarian breakthrough, the Serbian position became hopeless; their main army in the north faced either encirclement and enforced surrender, or retreat.[16]

Marshal Putnik ordered a full Serbian retreat, southwards and westwards through Montenegro and into Albania. The Serbs faced great difficulties: terrible weather, poor roads and the need for the army to help the tens of thousands of civilians who retreated with them. Only c. 125,000 Serbian soldiers reached the Adriatic coast and embarked on Italian transport ships that carried the army to Corfu and other Greek islands before it travelled on to Thessaloniki. Marshal Putnik had to be carried during the whole retreat; he died just over a year later in a French hospital.

French soldiers halting in Thessaloniki (1915).

The French and British divisions marched north from Thessaloniki in October 1915 under the joint command of French General Maurice Sarrail, and British General Bryan Mahon (Commander, British Salonika Force, 1915). However, the War Office in London was reluctant to advance too deep into Serbia. So the French divisions advanced on their own up the Vardar River. This advance gave some limited help to the retreating Serbian Army, as the Bulgarians had to concentrate larger forces on their southern flank to deal with the threat, which led to the Battle of Krivolak (October–November 1915).[17] By the end of November, General Sarrail had to retreat in the face of massive Bulgarian assaults on his positions. During his retreat, the British at Kosturino were also forced to retreat. By 12 December, all allied forces were back in Greece. The Germans ordered the Bulgarians not to cross the Greek borders, reluctant to risk a Greek entry into the war in response to a Bulgarian invasion in Macedonia. The Allies for their part took advantage of that, reinforcing and consolidating their positions behind the borders.[18]

Thus there resulted a clear, albeit incomplete victory for the Central Powers. As a consequence they opened the railway line from Berlin to Constantinople, allowing Germany to prop up its weaker partner, the Ottoman Empire. Despite the Central Powers' victory, the Allies managed to save a part of the Serbian Army, which although battered, seriously reduced and almost unarmed, escaped total destruction and after reorganising resumed operations six months later. And most damagingly for the Central Powers, the Allies—using the moral excuse of saving the Serbian Army—managed to replace the impossible Serbian front with a viable one established in Macedonia (albeit by violating the territory of an officially neutral country); a front which would prove key to their final victory three years later.[19]

Colonel Nikolaos Christodoulou, one of the leaders of the Greek National Defence Army, interrogates Bulgarian prisoners of war.

French gunners with 75 mm anti-aircraft gun in Thessaloniki.

Bulgarian major Ivanov with white flag surrendering to Serbian 7th Danube regiment near Kumanovo

On 30 May 1918, the Allies launched an offensive on the heavily fortified Skra salient, commencing the battle of Skra-di-Legen. The battle marked the first major Greek action on the Allied side in the war.[31] Utilizing the cover of heavy artillery a Franco-Hellenic force made a rapid push into the enemy trenches, conquering Skra and the surrounding system of fortifications. Greek casualties amounted to 434–440 killed in action, 154–164 missing in action and 1,974–2,220 wounded, France lost approximately 150 men killed or injured. A total of 1,782 soldiers of the Central Powers became prisoners of war, including a small number of German engineers and artillery specialists that served in Bulgarian units; considerable amounts of military equipment also fell into Entente hands. The plan for a Bulgarian counterattack against Skra remained unfulfilled as the Bulgarian soldiers refused to take part in the operation. Both the Greek and the French press used the opportunity to extol the efforts of the Greek army, favourably influencing the Greek mobilisation.[32][33][34]

The fall of Skra prompted Bulgarian prime minister Vasil Radoslavov to resign on 21 June 1918. Aleksandar Malinov who assumed office immediately afterwards pursued secret negotiations with Britain, offering Bulgaria's exit from the war with the condition that Bulgaria fully retain eastern Macedonia. However, British prime minister David Lloyd George rejected the proposal, assuring the Greek ambassador in London Ioannis Gennadius, that Britain would not act against Greek interests.[35]

With the German spring offensive threatening France, Guillaumat was recalled to Paris and replaced by General Franchet d'Esperey. Although d'Esperey urged an attack on the Bulgarian Army, the French government refused to allow an offensive unless all the countries agreed. General Guillaumat, no longer needed in France, travelled from London to Rome, trying to win approval for an attack. Finally in September, agreement was reached and d'Esperey was allowed to launch his grand offensive.[36]

The Allied forces were now large, despite the Russian exit from the war due to the Treaty of Brest-Litovsk in March 1918. Greece and its army (nine divisions) were fully committed to the Entente, while 6,000 Czech and Slovak former prisoners of war held on the Italian front were re-armed, re-organized, and transferred to the Macedonian front to fight for the Entente.[37] The Bulgarians had also increased their army during 1917, and in total manpower, the two sides were roughly equal (291 Allied battalions vs. 300 Bulgarian battalions, plus ten German battalions). However, as 1918 progressed, it was clear that the Entente had momentum the Central Powers lacked. Russian defeat had yielded no meaningful benefit to the Central Powers. The Ottoman Empire faced progressive loss of Arab lands. In Austria-Hungary, non-German and non-Hungarian parts of the multinational empire grew more openly restive. On the Western Front, intense German spring offensives had not defeated France, while American deployment was increasingly effective. Though Bulgaria and the United States were not at war with each other, German victory over the United States appeared conceptually infeasible. Finally, and most importantly for Bulgaria, almost all of its territorial war aims were already achieved, but as World War I was not merely a third Balkan War, Bulgaria could not quit. Alongside its partners, Bulgaria continued to suffer high casualties and civilian privation, including food shortages, seemingly to achieve the unrealized objectives of its allies. As a constitutional monarchy, Bulgaria depended on the consent of its people to keep fighting, while stress and discontent with the war grew.

The preparatory artillery bombardment of Bulgarian and Central Powers positions for the Battle of Dobro Pole began on 14 September. The following day, the French and Serbians attacked and captured their objective.[38] On 18 September, the Greeks and the British attacked but were stopped with heavy losses by the Bulgarians in the Battle of Doiran.[39] The Franco-Serbian army continued advancing vigorously and next day, some Bulgarian units started surrendering positions without a fight and the Bulgarian command ordered a retreat.[40]

In the official British government history of the Macedonian campaign, Cyril Falls wrote a detailed analysis of the situation of the Bulgarian forces and the situation of the front. Although a breakthrough was achieved at Dobro Pole and the allied forces continued their advance, the Bulgarian army was not routed and managed an orderly retreat. By 29 September (a day before Bulgaria exited World War I), Skopje fell but a strong Bulgarian and German force had been ordered to try and retake it the next day; the number of Bulgarian prisoners-of-war in allied hands around that day was only 15,000.[41]

Another major factor contributed to the Bulgarian request for an armistice. A mass of retreating Bulgarian mutineers had converged on the railway centre of Radomir in Bulgaria, just 30 miles (48 km) from the capital city of Sofia. On 27 September, leaders of the Bulgarian Agrarian National Union took control of these troops and proclaimed the overthrow of the monarchy and a Bulgarian republic. About 4,000–5,000 rebellious troops threatened Sofia the next day. Under those chaotic circumstances a Bulgarian delegation arrived in Thessaloniki to ask for an armistice. On 29 September, the Bulgarians were granted the Armistice of Thessaloniki by General d'Esperey, ending their war. The Macedonian front was brought to an end at noon on 30 September 1918 when the ceasefire came into effect. The Soldiers' Uprising was finally put down by 2 October.[42]

German Emperor Wilhelm II in his telegram to Bulgarian Tsar Ferdinand I stated: “Disgraceful! 62,000 Serbs decided the war!"[43][44] On 29 September 1918, the German Supreme Army Command informed Kaiser Wilhelm II and the Imperial Chancellor Count Georg von Hertling, that the military situation facing Germany was hopeless.[45] Tsar Ferdinand I of Bulgaria abdicated and went into exile on 3 October.

The British Army headed east towards the European side of the Ottoman Empire, while the French and Serbian forces continued north and liberated Serbia, Albania and Montenegro. The British Army neared Constantinople and with no serious Ottoman forces to stop it the Ottoman government asked for an armistice (the Armistice of Mudros) on 26 October; Enver Pasha and his partners had fled several days earlier to Berlin. The Serbo-French Army re-captured Serbia and overran several weak German divisions that tried to block its advance near Niš. On 3 November Austria-Hungary was forced to sign an armistice on the Italian front and the war there ended. On 10 November, d'Esperey's army crossed the Danube river and was poised to enter the heartland of Hungary. At the request of the French general, Count Károlyi, leading the Hungarian government, came to Belgrade and signed another armistice, the Armistice of Belgrade.[46]

Memorials erected in the area include the Doiran Memorial to the dead of the British Salonika Army.