A small group of historians consider the assassination of Franz Ferdinand by Gavrilo Principe, a member of the Young Bosnia organisation, as the immediate cause of the war. In addition, the Balkan wars are seen as a preamble to the First World War, and therefore the Balkan region gives an image of a conflict zone. This conviction has long prevailed in the historiography of the First World War. This interpretation largely neglects the processes and events that took place in Europe and throughout the world in the years and decades before the Balkan wars and the assassination of Franz Ferdinand. Today, it is generally accepted that economic elements, imperialism, rising nationalism, territorial conflicts, as well as the arms race and alliance-building are the causes of war. In the same way, and until the beginning of the war, two military-political alliances: the Entente (the United Kingdom, Russia and France) and the Triple Alliance (Austria-Hungary, Germany and Italy). Nevertheless, although Italy is part of the Triple Alliance, it did not join the central powers (Austria-Hungary and Germany) in the war. In addition to this, there are other interpretations that have fewer defenders but Franz Ferdinand's assassination and the crisis in July are most often considered to be the two main causes of the war. However, one of the main causes of this war would be the position of States that their national and state objectives could only be achieved through war, and that war was a legitimate means of achieving them. This is also the case for those who have publicly stated that they wanted a peaceful solution to the July crisis and for those who were against the war as a means of resolving the conflict in Serbia. As a result, state-sponsored societies and education have helped build this understanding and prepare the younger generations for conflict. It took a long time, and another monstrous war, the Second World War (1939-1945), to change this approach and conception of politics, state relations and the role of education in society.

Finally, Austria-Hungary's response to the attack in Sarajevo was sent on 23 July as an ultimatum, imposing a 48-hour deadline. The ultimatum was rejected by the Serbian government. This justified the declaration of war by Austria-Hungary on 28 July. Meanwhile, Russia was openly supporting Serbia. Russia had in mind that they would win in the case of a war against Germany, because they would have to fight on two fronts. On the other hand, the conflict between Germany and Russia and the weakening of German positions in Europe represented an interest for France. Taking this into account, Russia began a secret mobilisation of its armies on 24 July. On 31 July, Germany sent an ultimatum to Russia expiring within 12 hours in which it demanded that the Russian mobilisation be lifted. In the absence of a response, Germany declared war on Russia on the 1 of August. In addition, France mobilised its army. On 3 August, Germany declares war on France. Great Britain, still neutral at that time, mainly because of the civil war in Ireland, could not accept the domination of Germany. After the German invasion of Belgium and the rejection of the British ultimatum on 4 August, England declared war on Germany. Within a week, most of Europe was at war. In the following months and years, other European countries joined one of the belligerent alliances. In October 1914, the Ottoman Empire took the side of the central powers, Germany and Austria-Hungary, and the same month, in 1915, Bulgaria followed the same path. That same year, Italy decided to join the Entente. In 1916, Romania and, in 1917, Greece and the United States also joined the Entente. The war also spread to Asia and in the Pacific, where New Zealand and Japan invaded and conquered the German colonies, and in Africa for the same purpose.

Convinced that the war will not last long, Austria-Hungary was trying to invade Serbia without the help of Germany. It was on this front that the Entente won its first victory against the central powers. Due to several strategic errors of the Austro-Hungarian army led by General Oskar Potiorek, it suffered a defeat at Cer (Mountain of Serbia) in August 1914. Defeated, the Austro-Hungarian armies were forced to withdraw to the territories of Bosnia and Srem (now Serbia and Croatia). The second attempt of military victory over Serbia began on 7 September. After several fierce battles in which both sides suffered heavy casualties, the front line stabilized and entered trench warfare in a month and a half. This part of the war between Serbia and Austria-Hungary is also known as the Battle of Drina. After the Serbian army was weakened by trench warfare, General Potierek undertook a new offensive forcing the Serbian army to withdraw from the Kolubara River line. This battle is known as the battle of Kolubara. As a result of the battles of 2 December 1914, the Austro-Hungarian army entered Belgrade. However, the next day, the Serbian army launched a counter-offensive which forced the Austro-Hungarian army to withdraw into Bosnia and Srem. At the end of December, the Serbian army arrived at the borders of Austria-Hungary. The number of victims of these battles was significant on both sides, as well as the number of Serb civilians executed by the Austro-Hungarian army. The number of civilian casualties due to famine and typhus in the winter of 1915 was even higher. Until September 1915, in the Balkans, the warring parties remained silent. The focus had shifted to other fronts and diplomacy. Austria-Hungary was much more focused on the Russian and Italian fronts, and both sides were trying to acquire Bulgaria for a better offensive and better positioning in the Balkans. While waiting for the new offensive, Serbia tried to reorganize its army. However, armed war-related incidents took place on the territory of Macedonia, where VMRO armed groups attacked Serb armies in border regions along the Vardar River. The attack on Valandovo is particularly well known, also called the Valandovo affair or action. At the same time, and not far from the Balkans, in the spring of 1915, Allied forces from France, Great Britain and New Zealand attempted to disembark in the Dardanelles in order to conquer Istanbul and, subsequently, expel the Ottoman Empire from the war and weaken the central powers. The Allies suffered a major defeat and were forced to retreat to several Greek Aegean islands and Thessaloniki, where they tried to reorganize and assist the Serbian army in October, during the joint offensive by Germany, Austria-Hungary and Bulgaria against Serbia.

The large ground forces, accompanied by a large number of civilians without organized food, rushed south. This withdrawal made it difficult for Bulgarian forces to invade Macedonia and southern Serbia, which prevented the withdrawal by Macedonia. Attempts by the French and British armies along the Vardar River to Skopje and Kosovo to help their allies and facilitate their withdrawal were unsuccessful. Thus, the only option was to cross the high mountains of Albania in order to reach the shores of the Adriatic Sea. This trip was marked by many difficulties: inaccessible and difficult terrain, intense cold, hunger, occasional guerrilla attacks and poor logistics. All layers of the Serbian army and society, from the king to generals and officers, soldiers and ordinary citizens, took part in this long journey. At the beginning of December 1915, two large groups arrived as far as the flat parts of Albania: one in the Shkodra region and another in the region between Tirana and Elbasan. When they arrived at the seaside, they were disappointed by the lack of organized help from their allies. On the other hand, the Allies had to face important diplomatic problems, particularly because of Italy's territorial aspirations, which slowed down its support for Serbia. The French General Staff took some initiatives to help, but the process was slow. That is why, on 20 December, King Alexander personally addressed General Joseph Joffre, general officer of the French armies, with a request for immediate assistance without which part of the Serbian army would be captured or destroyed. Finally, the Entente forces decided to save their exhausted allies. General Jean de Montdésir, in charge of the operation, established a first coordination center in Brindisi. The ships, mainly French, were sent to Durres (for the sick and wounded) and Vlora (for the healthy soldiers). During the second half of January 1916, hundreds of ships with Serb troops began to arrive on the island of Corfu, designated as the main center for the collection, rehabilitation and reorganization of the Serbian army. On the smaller islands in front of Corfu, the Allies first performed medical examinations on the new arrivals, providing them with basic assistance, before sending them to the main base. By the end of February, more than 133,000 Serb soldiers had landed in Corfu. This success is at the same time a tragedy because it is said that during this difficult episode the Serbian army lost about 250,000 soldiers. Subsequently, those who managed to evacuate were actively involved in the battles of the Macedonian Front.

On the other hand, an important dichotomy existed among the main strengths of the Entente. Britain believed that without Greece on the side of the Entente, Serbia would be lost. While France believed that a significant military presence in the southern part of the Balkans was necessary, especially after the failure of the Dardanelles, for Romania and Greece not to join the central powers. At the same time, in Thessaloniki, the Allies began to build a military base and the British and French armies of General Maurice Sarrail were already present in the region. In December 1915, the French staff sent General Noël de Castelnau on a mission to the Balkans to examine the situation on the ground and the troops of the Allies, but also the possibility of developing the Macedonian Front. Six months later, General Sarrail was appointed commander-in-chief of the Allied army at the Macedonian Front, including the army stationed in Macedonia. This Allied army controlled about 30,000 square kilometres of territory. The population of this part of Macedonia was not hostile to the Allied army, but in view of the destruction caused by previous military conflicts, they distanced themselves from them. On the other hand, the Allies had doubts about the local population, very often considered to be dedicated to the Ottoman Empire and Bulgaria. Thessaloniki was at the centre of this area, a large cosmopolitan city with its history and a cross between cultures and ethnic groups (Jews, Turks, Greeks, Macedonians, Bulgarians, Vlachs, Roma and others), which had been included in the Greek state since 1912. After conducting analyses and drawing up additional plans, the Allied army deployed north of Thessaloniki, occupying a length of about 120 km. During the first half of 1916, the line of defence expanded increasingly, with various buildings and infrastructure managed by thousands of Allied soldiers and local civilians. Trenches, wells and canals were dug, wetlands drained, roads constructed and repaired. At the same time, thousands of French soldiers were transported by ships from Marseille and Toulon (South France) or even Otranto (Southern Italy) to the port of Thessaloniki. The Zeytinlik camp was the center of this military force, located 5 km northeast of Thessaloniki, near the Vardar River.

Although the agreement focuses mainly on the front in Italy, some of its provisions had a much wider impact and contribute to the general breakdown of the Triple Alliance forces. A few days earlier, on 30 October, in the port of Lemnos, the Ottoman Empire signed an armistice with the Entente, ending military action in the Middle East. On the Danube, where the Allied armies found themselves after the successes on the Macedonian Front, a new major offensive (from 9 November) was prepared against Mackensen's German army, again forced to withdraw through Hungary to Germany. Apart from these military events, and in order to understand the situation at that time, we need to focus on the internal context in Germany, which was very important. Due to the negative effects of the long war, citizens were dissatisfied: political unrest and demonstrations took place, the navy rebelled and refused to carry out its tasks (Wilhelmshaven, Kiel). All this triggered the November Revolution in Germany. On November 9th, Emperor Wilhelm II abdicated. Finally, on 8 November 1918, the military leaders of the warring parties met in the Compiègne forest (north-eastern France) and, after three days of negotiations, Germany accepted the conditions of the allies. The armistice was signed in the rail car of Marshal Ferdinand Foch, the commander-in-chief of the Allied forces, at 6 a. m., and came into effect at 11 a. m. Amongst other things, it was planned to withdraw German troops from Germany, exchange prisoners, destroy German warships and submarines, hand over German military equipment, stop German naval supplies, etc. It was also planned that the German troops would be able to return to Germany in the near future. Although the 11 November armistice ended the military operations, negotiations and the signing of a peace agreement were postponed until the following year. Numerous representatives of the warring parties participated in the International Peace Conference in Paris in 1919. The final peace was ratified on 10 January 1920. Today, November 11 is celebrated in many countries such as Armistice Day and the end of the First World War.