On October 5, 915, in accordance with the provisions of the military agreement between the three countries, the German and Austrian armies began their offensive. The Allied forces concentrated 1,700 heavy artillery pieces and 72 mine-throwers to prepare for artillery fire on the Serbian positions, and under the two-day artillery bombardment, 90 percent of the front-line positions of the Serbian army were destroyed, and the casualties were unusually high.

On 7 October, the Austro-Hungarian 3rd Army (7 divisions) on the right flank crossed the Drina River under the command of Austro-Hungarian General Covis.

Shortly thereafter, the German 11th Army (7 German divisions), commanded by General Gowitz, crossed the Danube and attacked Belgrade, supported by shallow heavy gunboats of the Austro-Hungarian Danube Fleet.

However, in the rubble-strewn and almost ruined city of Belgrade, the remnants of the Serbian troops put up a stubborn resistance, and these remnants from almost 27 different units spontaneously organized themselves and engaged in fierce and arduous house-to-house street battles with no backups.

Under the onslaught of the German-Austrian army, Belgrade fell on 9 October.

With the front line tight, the Serbian 2nd Army, which had been assembled on the Bulgarian-Serbian border in response to the Bulgarian general mobilization, began to reinforce the Serbian 1st Army and the 3rd Army against the German and Austrian armies.

So Bulgaria entered the war on October 13. The Bulgarian army, which had already been deployed on the left and right flanks, then attacked Serbia. The right flank attacked the southern front, Serbian Macedonia and Kosovo, while the left flank attacked Niš. Located in the northern part of the Morava River basin and in the southern part of the Vardar River basin, Niš is geographically important. It is located on the way to the main transport corridor between Greece and Central Europe, and the railway connecting Sofia and Istanbul also passes through here.

The occupation of Niš meant that the German-Austrian, Turkish-Bulgarian four countries were united, and it was a long drought for the Ottoman Turks, who were in dire need of German-Austrian arms replenishment, and the Ottoman Turks were fighting almost alone on four fronts in the Gallipoli Peninsula, Sinai, the Caucasus, and Mesopotamia, which was busier than the Austro-Hungarian Empire.

Although the Bulgarian 1st Army had the largest number of troops and the best equipment, the Serbian army it faced was not strong, and its strength was less than half that of the Bulgarian 1st Army. However, due to the unfavorable conditions such as the preset Serbian fortress group in the Piro area, the harsh climate that caused the roads to be very muddy, and the frequent fog that made visibility extremely low, the early progress was not fast. It was not until 5 November that the 1st Bulgarian Army finally captured Niš.

Compared to the slowness of the 1st Army, the Bulgarian 2nd Group performed best as a partial division. On October 16, 1915, that is, only three days after Bulgaria entered the war, the 2nd Army occupied the town of Van Ranje, which is located in southern Serbia, directly east of the Kosovo region, because it is a station on the Belgrade-Thessaloniki railway.

The offensive of the 2nd Army was very smooth and overwhelming. Kumanovo was captured on October 20, and Skopje, the largest city in Macedonia, was captured on October 23. One third of the total population of Serbian Macedonia lives here, and it is the political, cultural, economic, and academic center of Macedonia. During the Ottoman period, the city was named Üskup, which was later renamed Skopje by the Serbs.

October 5, 1915 seemed to be a meeting point of fate, and the rest of the Balkans was not quiet, and other countries in it were like moths to a fire, and one by one they were involuntarily involved in the world war.

It was also on this day that King Constantine I of Greece once again dismissed Eleftherios Venizelos as prime minister, delaying Greece's entry into the Entente for almost another two years. From the perspective of relatives, the British and German Russian royal families are quite close in blood, and this does not prevent the life and death between countries and nations.

Prime Minister Venizelos was an active advocate of joining the Entente in the war from the outset, and under the 1913 Treaty of the Cyscom-Greek Alliance, when either side was attacked by Bulgaria, the other side was obliged to enter the war, and Constantine I maintained neutrality on the grounds that the attacking party was Austria-Hungary, not Bulgaria. In fact, Konstantin I was pro-German, his wife was the sister of Kaiser Wilhelm II, and accepted the honor of Marshal of the German Reich on August 8, 1914, when the war had just begun.

On the same day, the Allied forces with the French army as the main force landed in the then neutral Greek port of Parallha in the name of supporting Serbia, and more and more Allied troops gathered around Paralia, and finally formed the fourth major front in the European theater of World War I - the Macedonian Front, on which Bulgaria was almost independently supported.

As soon as the French landed, they disarmed the Paraglia batteries and took over the entire port, and the Allies were a gross violation of Greek neutrality by not participating in the war at the time. Britain's reason for entering the First World War was that Germany had grossly violated Belgian neutrality through Belgium, and there was no moral condemnation of the French army's actions.

There is a direct railway from Thessaloniki to Belgrade, and if the three divisions of the French army that landed immediately plunged into the attack on Thessaloniki from Paralia, then not only would it effectively support Serbia's war of resistance in terms of manpower and material resources, but it would also mentally stimulate the morale of the Entente countries to hate the same enemy, and it would definitely have the effect of allocating thousands of dollars. It's just that the French army stopped in Paralia and stopped inexplicably.

At this time, the Bulgarian 2nd Army, which was attacking the Macedonian region, immediately moved its left flank to the line of Thessaloniki to defend against a possible French attack. At the same time, Bulgaria mobilized 3 divisions from the country to the front line of Salonika, so Bulgaria formed the 2nd Army Plain Cluster in the Salonika Plain, and defeated the 4 divisions of the Entente (3 divisions of the French army and 1 division of the British army) who came to seize Salonika with 6 divisions.

The Bulgarian 1st Army captured Niš and opened the way for Germany and Austria to support the Ottoman Empire, and Germany's main goal had been achieved, and it began to transfer troops to the Eastern Front.

The Serbian army, under the command of the old commander Putnik, was defeated but not chaotic, and while retreating, the walls were cleared, the war supplies were burned, and the roads were destroyed along the way.

All the bridges on the Morava River on the way of the 1st Bulgarian Army were blown up by the Serbian army, and it took a lot of effort to cross two divisions, and the German-Austrian army was the same, and the weather and roads caused logistics to be unable to keep up, which affected the delivery of troops and firepower.

Marshal Mackensen's three-pronged plan to gather and annihilate the Serbian army on the Kosovo plain became a paper battle, but it gave Serbia a fleeting opportunity.

In 1915, the last major battle of the Serbian campaign, the Battle of Kosovo, began. With Pristina in Kosovo as the axis, the Serbian army was preparing to break the Allied forces one by one with the advantage of the inner line.

Initially targeting the Bulgarian 1st Army, it launched an offensive against the Bulgarian forces in the direction of Niš, northeast of Pristina, and within two days captured Pfrepje in southern Serbia.

Then, with a clockwise right-hand turn, he launched a blow to the northern cluster of the Bulgarian 2nd Army, which had already invaded Kosovo. In Granine, the Bulgarian 2nd Army went north to cluster and Serbia engaged in heavy battles. Both sides suffered heavy casualties, and in the end Serbia ended with more than 30,000 casualties and 200 artillery pieces captured.

On November 23, the German 101st Division and the 9th Division of the Bulgarian 1st Army entered Pristina, the capital of Kosovo, without bloodshed, but the main Serbian army had already crossed the Stinka River to escape the German-Austrian and Bulgarian pursuits.

On November 25, the commander-in-chief of the Serbian army, Putnik, issued a general retreat order, and the Serbian army crossed the mountains in four routes, retreated to the ports on the Adriatic coast of Albania, and was picked up by the Allied fleet and placed on the Greek islands.

The first route starts from Kosovo Mitrovica via Montenegro - Albanian Shkoder-Durrës.

The second route starts from Pristina via Pec ---- Albanian Leš-Durres.

The third route also runs from Pristina via Prizren --- Albanian Tirana - Durrës.

The fourth road was the remnants of the Macedonian army, which departed from Struga --- Albanian land of Perat-Vlora.

So Serbia invaded the neutrality of the small new state of Albania. Moreover, at that time, the Serb soldiers and civilians were cold and frozen, and lacked food and clothing, so it was natural to recruit them from Albania. For the people of Albania, this is a group of bandits who loot their belongings.

420,000 Serb soldiers and civilians fled, and the Serb soldiers and civilians who were finally picked up from Albania by the British and French fleets arrived in Greece at 260,000, of whom 155,000 soldiers, many of whom died in the Greek islands due to exhaustion and infectious diseases (mainly typhoid fever).

The Serbian campaign ended in 1915 with Bulgaria ending skirmishes with the British on 12 December and occupying the entire Greek-Serbian border.

A total of 424,375 Bulgarians were involved in the battle, with 37,000 casualties, including 24,000 casualties of the 2nd Army. The result was more than 90,000 Serbian killed and 174,000 captured.

Now that the whole of Serbia has been divided between Austria-Hungary and Bulgaria, they are satisfied with the results of this time, and now they only need Bulgaria to defend the Macedonian line. This time, apart from the worst occupation of Montenegro and Serbia, Greece is the most tragic neutral country. The two camps completely ignored the neutrality of Greece and fought in Greece at will. In particular, Britain and France not only occupied Greek ports, but also forcibly used Greek islands to house defeated Serb soldiers and civilians.

PS； Today's update is complete, and the steamed buns are at home these days, so the update can't be stable, I hope you forgive me.