World War I: Start, Causes, Development, Consequences

The First World War was a warlike conflict that affected all the great political and military powers of the time. The war began on July 28, 1914 and ended on November 11, 1918.

The First World War was also known as the Great War, a name that it maintained until the outbreak of the Second World War . Historians estimate that between 9 and 10 million deaths occurred and nearly 30 million people were injured.

The war was the result of a series of political and military events that took place throughout the nineteenth century, especially after the Franco-Prussian War ended. The powers of the time signed different military alliances in what is known as Armed Peace .

To these alliances must be added the growth of nationalism in many countries, the struggle to expand colonies and empires, as well as commercial rivalries between all nations. The result was a division into two great coalitions: the one formed by the great Central Empires (Triple Alliance) and the one created by the allies of the Triple Entente .

After decades of tension, the event that led to open warfare was the assassination in Sarajevo of Archduke Franz Ferdinand of Habsburg, heir to the throne of the Austro-Hungarian Empire.


The trigger for the outbreak of the First World War was the assassination of the heir to the throne of the Austro-Hungarian Empire. However, that was only the latest of the events that led to the conflict.

The antecedents must be framed in a context of permanent friction between the great powers of the time caused by their imperialism and their desire to acquire the greatest possible power.

The Franco-Prussian War

The Franco-Prussian War ended with the French defeat in 1870. This caused a shift in the European balances of power. Germany completed its unit and William was recognized as Emperor.

France, on the other hand, lost some territories to its enemy. The humiliation suffered, the desire to recover Alsace and Lorraine, and its intention to return to being a great power caused its relations with Germany to be very tense and were always on the brink of conflict.

Alliance system

Once Napoleon was defeated, the European powers began a game of alliances and strategies that lasted throughout the 19th century and the first years of the 20th. Its beginning can be marked in the formation of the Holy Alliance between Prussia, Austria and Russia in 1815, but it was later when it reached its peak.

The fundamental figure to understand that time was the German Chancellor Otto von Bismarck. In 1873 he promoted an alliance between Austria-Hungary, Russia and Germany, the three most important monarchies of the moment. Russia soon withdrew from the agreement due to its differences with Austria-Hungary over the Balkans, some constant until the Great War.

Germany and the Austro-Hungarian Empire did continue in the alliance, which was joined by Italy in 1882 (Triple Alliance). With the withdrawal of Bismarck and the arrival to the throne of Guillermo II, its system of agreements began to weaken, although certain agreements were maintained.

The other powers also made strategic moves. France, still suffering the consequences of its lost war with Prussia, signed an agreement with Russia to counter the Triple Alliance.

For its part, the United Kingdom also signed treaties with France, forming the so-called Entente Cordial. Later, it did the same with Russia.

La Paz armed

The aforementioned policy of alliances resulted in the time known as La Paz Armada. All the powers began an arms race in order to reinforce their armies. It was a matter, first, of dissuading their rivals from initiating hostilities and, second, of being prepared should war break out.

Germany built a powerful Imperial Navy, with the pretense of standing up to the English naval might. These replicated modernizing their ships. Something similar was going to happen with the other nations and with all kinds of military equipment. Nobody wanted to be left behind.

According to historians, between 1870 and 1913, Germany and England doubled their military budgets, France doubled them, and Russia and Italy significantly expanded them.

Colonial Imperialism

The final decades of the 19th century and the first decades of the 20th century were the time when colonialism became imperialism . All the powers, including Japan and the United States, had colonies in Africa and Asia. Trade, cheap labor and raw materials were the main arguments to keep them.

Despite the fact that there were revolts in the colonized countries, the most important problems for the colonizing powers came from the struggle with other powers to increase the occupied territories.

The balkans

The Balkan area had always been the cause of conflict between the great powers. When the Ottoman Empire weakened, they all tried to take its place and gain influence in the area.

It was Austro-Hungary that started the so-called “Bosnian Crisis”, by annexing Bosnia and Herzegovina. The Serbs reacted angrily. Russia, as a Slavic and Orthodox country (like Serbia), began to maneuver diplomatically. The region became even more destabilized and became known as “Europe’s powder keg.”

The First Balkan War was fought between 1912 and 1913 and pitted the Balkan League and the Ottoman Empire against each other. The latter were defeated and lost even more territories. Instead, Serbia, Montenegro, Greece and Bulgaria gained ground and Albania was created.

With little margin, the Bulgarians attacked Serbia and Greece in June 1913, leading to the Second Balkan War. On this occasion, it was the Serbs, the Greeks, the Romanians and the Ottomans who ended up gaining territories.

In both conflicts, the great powers remained relatively on the sidelines, so the contest was not extended. However, the tension continued to rise steadily.


The outbreak of the First World War finally occurred on June 28, 1914. That day, Archduke Franz Ferdinand of Austria, heir to the throne, was visiting Sarajevo, Bosnia. There, a group belonging to Young Bosnia, a nationalist group that advocated union with Serbia, had organized a plan to assassinate him.

As the archduke’s entourage passed, one of the conspirators threw a grenade at his car. However, he did not achieve his goal.

An hour later, Francisco Fernando’s caravan mistakenly headed down a city street. As chance would have it, one of the young men from the attacking group, Gavrilo Princip, was found. He took advantage of the opportunity and, with his pistol, ended the life of the nobleman.

The Austro-Hungarian government reacted by fueling anti-Serb riots in Sarajevo itself, with several Serb people killed by Croats and Bosnians. In other cities there were also riots and attacks against Serbs, in addition to those arrested in the different organized raids.

July crisis

The month after the assassination was critical for the war to begin. All the powers began to maneuver diplomatically, first, and militarily later.

Austria-Hungary accused Serbia of being behind the crime and announced an ultimatum on July 23 with ten demands that could not be met by the Balkan country. The next day, Russia proceeded to mobilize all its troops.

On July 25, Serbia did the same with theirs and answered the Austro-Hungarian ultimatum: it accepted all their demands except the one demanding that the Austrians participate in the murder investigation.

The Austrian response was immediate: it broke diplomatic relations with Serbia and ordered the mobilization of the army. Finally, on the 28th the Austro-Hungarian Empire declared war on the Serbs.

Mobilization of Russia

As an ally of Serbia, Russia mobilized its army against Austria-Hungary, which provoked a reaction from Germany, their ally. The German Kaiser, Wilhelm II, tried to mediate with the Tsar, then his cousin. However, he refused and Germany issued an ultimatum demanding the demobilization of Russian troops and not supporting Serbia.

At the same time, the Germans sent another ultimatum to the French not to help their ally Russia in the event of war.

On August 1, Russia responded by refusing German requests, which reacted by declaring war on it. On the 4th, Austria – Hungary mobilized all its troops.


France failed to respond to the German ultimatum. However, she withdrew her soldiers from the borders to avoid incidents. Despite this, she had all her reservists mobilized and Germany responded by doing the same.

The Germans, trying to avoid the French attack, went ahead and invaded Luxembourg. On the 3rd, she formally declared war on France. The next day she also declared it to Belgium, which refused to allow the passage of its troops on the way to the French border.

The last uninvolved great power, Great Britain, required Germany to respect Belgian neutrality. Faced with the refusal, he decided to declare himself in a state of war.


The Great War involved, for the first time, all the political and military powers of the planet in a warlike conflict. Many historians highlight five main causes for that situation.


The great European powers embarked on an arms race during the Armed Peace. The development of the war industry seeking to control international trade was especially prominent in Great Britain and Germany.


Africa and Asia had become the object of desire for the great powers. The struggle to control their natural resources led to clashes between the colonizing nations.

As an example of this, Germany’s attempt to build a railway line between Berlin and Baghdad, to control the Middle East, caused a considerable increase in tensions with Russia.

Territorial claims

The confrontation between the powers was not only due to the colonial territories. They also arose from old unresolved territorial disputes, such as the one between Germany and France over Alsace and Lorraine.

Something similar happened with the Balkans, where Russia wanted to become the defender of the Slavs and Orthodox.


Nationalism, as an ideology that sustained the existence of nations, grew in a very remarkable way at that time. It was also a question of a nationalism often ethnicist, as when Germany declared its claim to create an empire with all the countries of Germanic origin.

Something similar happened with Russia and its Pan-Slavicism, although it was content to appear as the defender and guardian of the different Slavic peoples.

Alliance Policy

The alliances created during the Armed Peace, and even before, caused different nations to enter the war to fulfill their commitments.

In general terms, there were two large blocks of alliances: the Triple Alliance and the Triple Entente, although there were variations over the years.


The British, among other nations, won the First World War

At first, in the Great War only the European powers, their allies and colonies participated. The subsequent entry into the conflict by the US and Japan turned it into a world confrontation.

The Triple Alliance

The central members of the Triple Alliance were the Austro-Hungarian Empire and the German Empire. They were joined by Italy, although when it entered the war it did so supporting the other side. Other nations, such as Bulgaria and the Ottoman Empire also lent their support to this bloc.

The Austro-Hungarian Empire was the country that first declared war. This caused the signed defense agreements to be activated, causing the expansion of the conflict to the entire continent. Its defeat meant the disappearance of the Empire and the independence of several territories that had made it up.

For its part, the German Second Reich, under the command of William II, soon came to the aid of its Austro-Hungarian ally. In addition, with this he had the opportunity to once again face his traditional French rival and try to invade him.

The Triple Entente

At first it was made up of the United Kingdom, France and the Russian Empire. They were eventually joined by the United States, Romania, Serbia, Greece and Italy.

In the case of France, it was still suffering the consequences of its defeat with Prussia decades ago. Its defense treaty with Russia caused that, when it declared war on Austria-Hungary, it immediately joined the hostilities.

The United Kingdom, for its part, was more interested in the maintenance and expansion of its colonies than in continental politics. When Germany invaded Belgium, he realized that his interests could be threatened and he proceeded to declare war.

Russia was Serbia’s main ally and therefore proceeded to support it from the start. However, the 1917 Revolution caused him to abandon the conflict before it ended.

Finally, the United States maintained its neutrality for several years. The sinking of the Lusitania by Germany caused the death of more than 100 Americans, but it was the German attempt to convince Mexico to attack the country that made it enter the war.


July 28, 1914 was the start date of the First World War. Millions of people died during the years the fighting lasted.

At first, the forces of both blocks were very even in terms of the number of soldiers. However, there were differences in resources and equipment. As an example, historians point out that the Triple Entente did not have any long-range guns, but they did have naval superiority.

War of Movements

The first military movements were based on fast and very effective attacks. Germany had developed a plan called Schlieffen with the aim of invading France and reaching Paris in a very short time. For their part, the French devised Plan XVII, which sought to recover Alsace and Lorraine.

Both plans ended in failure and the situation at the front stalled. A great front of trenches formed, without anyone advancing far enough.

Russia, in those early stages, attacked Austria and Germany from the east, and the Austro-Hungarian Empire attempted to occupy Serbia.

Trench war

Despite the planned plans, all participants understood that the war was not going to be short. Germany entrenched itself on the western front, trying to preserve what it had conquered. The Hindenburg Line had 700 kilometers of trenches that separated France from the German army.

During this period new participants were incorporated. The Ottoman Empire and Bulgaria did it in favor of the imperial powers and Romania and Italy to the allies.

It is in the Balkans where the most news was produced. Russia, with internal problems, had to withdraw many men and the different Balkan territories repeatedly changed hands.

Crisis of 1917

After three years of war and with a rather stagnant situation, all the participants suffered internal problems due to the opposition of their citizens.

In France, which was immersed in a bloody trench warfare and with a lack of food, there were industrial strikes and uprisings in several towns. In Britain, the people were also tired, although protests were minor.

Political differences began to appear in the German Empire, with supporters ending the conflict.

The Austro-Hungarians, for their part, had to fight on two different fronts. In addition, numerous separatist revolts broke out in much of its territory.

Finally, the Russian Revolution broke out that year. The triumph of the Bolsheviks caused the country to abandon the war.

Turn of war

It was in 1917 that the United States joined the First World War. At that time, the different open fronts were very stagnant. Practically all of them limit themselves to resisting, without having the ability to defeat their enemies.

The American entry, in 1917, gave new strength to the Allies of the Triple Entente and was vital to the outcome.

End of the war: Victory of the Allies

In the last months of the war, the contestants were very weakened, both in the military and because of the internal opposition in each country. This affected the two imperial powers in a special way, since the Allies were greatly benefited by the incorporation of the United States to their side.

One of the last attacks against the Austro-Hungarian Empire took place from the south, after the landing of the allied troops in Greece. From that moment on, Austria-Hungary began to crumble, with successive declarations of independence for its territories. By November 1918, only Austria remained of the old Empire.

The defeat left Germany without any support and, on the western front, the Allies managed to defeat it. On November 11, 1918, she surrendered to her enemies.


The map of Europe underwent a radical change. Four empires disappeared in that war: the Austro-Hungarian, the German, the Ottoman and the Russian. This caused many new nations to appear and others to regain their independence.

Loss of life and destruction

The magnitude of the First World War caused some 10 million people to die. Another twenty million soldiers were injured. An estimated 7 million civilians died.

These figures represented a brutal demographic crisis in the belligerent countries. Not only because of the dead, but because of the number of orphans and widows that it supposed.

Apart from human lives, the continent’s infrastructure was devastated, especially in northern France, Serbia and Belgium. The victors tried to make the defeated pay for reconstruction, but it was impossible.

Great Britain became one of the most indebted countries and hyperinflation hit Germany. The only nation that benefited was the United States, which became a great power in the face of the decline of the Europeans.


Territorial changes were not limited only to the disappearance of empires. Thus, the German and Turkish colonies passed into the hands of the victors, especially France and Great Britain.

The French were also able to recover Alsace and Lorraine, in addition to annexing the German area of ​​the Rhine.

Even before the end of the war, when Austria-Hungary was falling apart, Czechoslovakia was formed. Besides, Hungary got its independence. With the defeat and disappearance of the ruling house in the Empire, the allies created the Republic of Austria, with a very reduced size due to the losses of territory at the hands of Romania and Serbia.

Taking advantage of the conjunctural weakness of the newly created Soviet Union, the allies promoted the appearance of several countries as barriers to communism: Lithuania, Latvia, Finland and Czechoslovakia itself.


Historians point to times of famine and economic depression across the continent. The entire war industry had to be converted into other types of factories, although it took a long time.


Peace Treaties

The losers and the winners signed several different peace treaties when the war ended. In them the conditions that the defeated powers had to fulfill were established.

The first, and the one with the most consequences, was the Treaty of Versailles. It was signed on June 28, 1919 between the Allies and Germany. This country was forced to demilitarize, its colonies were transferred to other countries, it had to submit to international supervision, and it was condemned to pay huge amounts in compensation.

The conditions imposed caused a feeling of humiliation in Germany. Ultimately, it became the seed for the emergence of the Nazi Party and the following World War.

The Treaty of Saint-Germain , in Laye, was the next to be negotiated. It was sealed on September 10, 1919 and involved the victors and Austria. Through it, the Empire was dismembered and the Habsburg monarchy disappeared.

In addition, the loss of territories of the Ottoman Empire and the new borders of the Balkan area were also decided in other treaties.


Although Austria-Hungary had started the conflict, Germany was the country that suffered the most from its consequences. The republic that succeeded Kaiser Wilhelm II was born in a context of economic and social crisis. Left and right groups promoted numerous uprisings and social tension was constant.

Ultimately, that situation was the perfect breeding ground for the emergence of the Nazis. Hitler, who blamed Communists, foreigners and Jews for the surrender of his country in the First War, ended up seizing power by promising to make Germany great again.

Only two decades after the end of the Great War, World War II began, with even more bloody results than the previous one.


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