World War I occurred from 1914 until 1918 and was one of the most significant events of the 20th century. At the time, it was referred to as the ‘Great War’ or the ‘War to End All Wars’. Today, it is remembered as one of the deadliest conflicts in human history. For instance, historians estimate that over 21 million deaths resulted from World War I, including 8.5 million soldiers and 13 million civilians. Besides this, World War I is also important because it created the atmosphere that led to other events, including: the Russian Revolution, the Spanish Flu of 1918 and World War II.​
Causes of World War I
World War I began in July of 1914, and is considered to have five major causes that led to the outbreak of the war. These five causes include the four long-term causes (militarism, alliances, imperialism and nationalism) and one short-term cause (the assassination of Franz Ferdinand).​
The four long-term causes each occurred in the years and decades before the actual outbreak of World War I, and all combined to set the stage for war in 1914. Most people think of these as the ‘MAIN’ causes of World War I.​
​MilitarismThe buildup or expansion of a country’s military power and ability to wage war. can best be understood as the buildup or expansion of the ability of a country’s military to wage war. In the decades before World War I many European countries began to practice militarism and worked to expand and strengthen their military forces. For example, there was an intense arms race and naval race between several European nations in the buildup to World War I.
The second long-term cause of World War I was the system of alliances that existed in the years before the outbreak of war in 1914. When World War I began, Europe was divided between two separate alliance systems. Britain, France and Russia made up the Triple Entente while Germany, Austria-Hungary and Italy made up the Triple Alliance. Both sets of alliances were created in the years and decades before World War I between the partnering countries. The assassination of Austro-Hungarian archduke Franz Ferdinand and the resulting crisis between Serbia and the Austro-Hungarian Empire caused each system of alliances to activate, and World War I began. Ultimately, the alliance systems that existed before the start of World War I obligated countries to go to war in defense of their allies. This obligation is how countries such as Britain, France and Germany were pulled into the conflict. Italy, although a member of the Triple Alliance, stayed neutral in 1914 and later joined the Allies in May of 1915.​
The third main cause of World War I was European imperialismA process where one country takes over another country or region’s political, economic, or social life. that occurred in the 1800s and early 1900s before World War I erupted in 1914. Imperialism is understood as a process in which a country overtakes another country or region’s political, economic or social life. Imperialism was carried out by the powerful European nations against the rest of world in the decades before World War I began. For example, in the 19th century European nations carried out massive campaigns of imperialism against the regions of Africa in an event known as the Scramble for Africa. The Scramble for Africa led to the start of World War I because it increased rivalry between the European nations as they fought against each other for territory in Africa and control over different regions.​
The fourth and final long-term cause of World War I was the growth of nationalism that occurred in Europe in the decades before World War I and the tensions it caused. NationalismWhen a group of people share a strong loyalty and sense of identity with their nation or country. is best understood as when a group of people identify with each other and display a loyalty to their nation or country.​
​Nationalism grows when people share similar beliefs, values, ethnic heritage, relationship to land, language, culture and customs. Nationalism was a major cause of World War I because it caused tensions and unrest to grow in certain parts of Europe. For example, the Austro-Hungarian Empire was not made up of one single nation, but rather consisted of many different groups. Many of these groups sought to have control over themselves and wanted sovereignty from the rule of the Austro-Hungarian Empire. This created a great deal of unrest in the empire. This was especially apparent in the Balkans, which is a region in Southeast Europe that contains many different nation-states.
The assassination of Franz Ferdinand was the main long-term cause of World War I.
Assassination of Franz Ferdinand
Franz Ferdinand was the Archduke of Austria-Hungary and the heir to the Austro-Hungarian throne in the years before World War I. Ferdinand and his wife Sophie were assassinated on June 28th, 1914 in Sarajevo, the capital of the Austro-Hungarian province of Bosnia and Herzegovina while there on a visit to inspect the military forces. The assassin was a Serbian nationalist named Gavrilo Princip. Just nineteen years old at the time, Princip was a member of Young Bosnia, a group that was armed and trained with help from the Black Hand.
The Black Hand was a Serbian nationalist organization that existed in the early part of the 20th century. The Black Hand was first created in May of 1911, by members of the Royal Serbian Army. It was a secret society that worked to promote Serbian nationalism. They were opposed to Austro-Hungarian influence in the Balkans, which was the name for the southeastern region of Europe. As such, the Black Hand helped plan the assassination of Franz Ferdinand as a form of protest towards Austria-Hungary.​​
The assassination of Franz Ferdinand and his wife Sophie caused the nationalistic tensions of the Balkans to spill over and the event is considered to have directly led to the outbreak of World War I. In fact, the assassination of Franz Ferdinand was a direct cause of the ‘July Crisis of 1914’, which saw tensions escalate between the major European powers to the point that it resulted in World War I. For instance, the July Crisis of 1914 was the immediate result of the assassination and saw Europe divided along the two major series of alliances (Triple Entente and Triple Alliance). A month after the assassination, World War I had begun. As such, the assassination of Franz Ferdinand was a vitally important event that changed the course of history in the early 20th century.​
FactsthatCrunch
Trenches of World War I
World War I was a global conflict that was fought on several fronts, including the Western Front, Eastern Front, Italian (Alpine) Front and the Middle East. The armies of World War I fought across the many different fronts of the war, which resulted in the many famous and deadly battles of the First World War. In fact, over 70 million soldiers were mobilized by the nations of World War I across the different fronts. Much of the fighting on these fronts occurred in the famous trenches of World War I.
World War I was characterized most dramatically by the nature of trench warfare. In general, trench warfare involved two opposing armies digging trenches in the Earth that faced each other. The armies of World War I did this in order to avoid gunfire from the enemy forces and to await their own orders to attack ‘over the top’ of the trench. Deadly weapons such as tanks, poison gas, machine guns and artillery were used in World War I, which contributed to the casualties of the war.​
FactsthatCrunchTrench warfare was a system of fighting in World War I where opposing armies dug long ditches into the ground to shelter soldiers and hold a fixed battle line.
Western Front of World War I
The Western Front of World War I was the line of fighting that occurred in the trenches that stretched through parts of Belgium and northern France. It was named the ‘Western Front’ due to it occurring in western Europe. The Western Front developed following the failure of the German plan of attack (Schlieffen Plan) at the beginning of World War I, which forced Germany to fight a two-front war against the Allied Powers. The Western Front was the major scene of fighting between Germany and the Allied Powers of France and Britain. Other Allied forces that participated on the Western Front included Australia, Belgium, Canada, United States, and New Zealand.
In all, the Western Front was likely the most famous of the fronts and led to some of the biggest battles of the entire war. For instance, the Battle of the Somme and the Battle of Verdun were both incredibly deadly and devastating battles. The Battle of the Somme saw over 1 million casualties, while the Battle of Verdun was equally terrible. The Battle of Verdun is remembered today as the longest single battle in human history. The battle lasted 302 days and caused devastating casualties for both the French and the Germans. For instance, historians estimate that France suffered as many as 400,000 casualties and 163,000 deaths. As well, it is estimated that Germany suffered as many as 350,000 casualties and 143,000 deaths.​​
Eastern Front of World War I
The Eastern Front of World War I was the line of fighting that occurred along the eastern border of Germany with Russia. The Eastern Front was the major scene of fighting between the Central Powers of Germany and Austria-Hungary against the Allied Power of Russia.​ The Eastern Front also formed following the Russian advance on East Prussia, when the Russian armies faced off against the German Army in the Battle of Tannenberg. The battle occurred in late August 1914 and set the stage for the line of fighting between Germany and Russia, which became known as the Eastern Front. Another important aspect of the Eastern Front was the southern portion, which was primarily fought between the Russian Army and the Austro-Hungarian Army.​
FactsthatCrunchWhy Did the Eastern Front of World War I Form?
The Eastern Front formed after Russia launched an advance into East Prussia in August 1914, forcing German and Austro-Hungarian armies to fight along Germany's eastern border. The Battle of Tannenberg, fought in late August 1914, set the stage for this line of fighting between the Central Powers and Russia. The southern portion of the Eastern Front was fought mainly between the Russian Army and the Austro-Hungarian Army, making it an overall conflict that went beyond a Germany-versus-Russia battle.
Russian Revolution and World War I
​As stated above, World War I took place from 1914 until 1918. During that time, the war was often characterized as a ‘stalemateA situation in war where neither side makes meaningful progress against the other.’, meaning that neither side made much progress. This is best evidenced by the terrible losses experienced by the armies of World War I, and trench warfare. For instance, a key feature of trench warfare was how little movement the armies made against each other. In fact, it was common for countries to send thousands of their own soldiers to their death with little or no gains on the battlefield.  This situation led to the terrible casualties of World War I and continued until near the end of the war.​
With that said, significant events near the end of the war caused the fighting to change dramatically and eventually led to the end of World War I. One of these events was the Russian Revolution, which reached its height in 1917. At the time, Russia was led by a Tsar, which was the title for Russian absolute monarchs before 1917. Tsar Nicholas II ruled over Russia before and during the first parts of World War I. The mounting Russian casualties and lack of supplies led to an increased amount of anger directed at the Tsar and his handling of the Russian war effort. At the same time, Russia was a society that was sharply divided, and the poorest Russians struggled to survive day-to-day. Poverty was widespread, especially among Russian peasants, who worked for the landowning nobility. This all combined to set the stage for a revolution against the Tsar and his rule over Russia.
​In 1917, Vladimir Lenin led a series of revolts against Tsar Nicholas II. Lenin was the leader of the Bolsheviks, who were a communist organization that sought to gain power over Russia and to pull Russia from the fighting in World War I. Soon, Tsar Nicholas II and his family were imprisoned and Lenin and the Bolsheviks assumed power over Russia. In the end, the Russian Revolution forced Russia to withdraw from the fighting.
​Russia’s withdrawal from the fighting in World War I was a tough blow for the Allied Powers, because it now allowed Germany to focus all of its forces on the Western Front. However, the French and British would soon receive much needed support when the United States officially joined World War I on the side of the Allied Powers.
FactsthatCrunchItalian Front of World War I
​The Italian Front of World War I was the line of fighting that occurred along the northern border of Italy with Austria-Hungary. The Italian Front was also referred to as the ‘Alpine Front’ because much of the fighting took place in mountainous regions and along valleys in the Alps. The Italian Front developed when Italy joined the war effort in 1915 and continued until 1918 when World War I ended. During that time, the Italian Front primarily resulted in fighting and battles between Italy and Austria-Hungary.​
The Italian Front was not as large or complex as the Western Front or Eastern Front but it was the site of some significant battles of World War I. For example, the most significant battle of the Italian Front is the Battle of Caporetto. Other significant battles of the Italian Front included the Twelve Battles of Isonzo and the Battle of Vittorio Veneto. In fact, the Battle of Caporetto was the Twelfth Battle of Isonzo.
FactsthatCrunchWhich two sides fought on the Italian (Alpine) Front of World War I?
Gallipoli Campaign of World War I
​The final major ‘front’ of World War I occurred in the Middle East between the Ottoman Empire and the Allied Powers. For instance, the Gallipoli Campaign was one of the most famous examples of conflict in the Middle East during World War I. The Gallipoli Campaign was a major conflict in World War I and occurred on the Gallipoli Peninsula in modern-day Turkey. It was primarily fought between the Allied Powers of Britain and France against the Central Powers of the Ottoman Empire and Germany.
Today, the Gallipoli Campaign is remembered as one of the most significant events of World War I. For example, it is of particular importance in the history of Australia and New Zealand. This is because both of the nations participated in the Gallipoli Campaign as part of the British Empire.​  Also known as the ‘Dardanelles Campaign’, the Gallipoli Campaign took place from February 19th, 1915 until January 9th, 1916.
FactsthatCrunchAllied Troops Land on Gallipoli, Opening the Land Campaign
At dawn on April 25th, 1915, British, French, Australian, and New Zealand troops landed on the Gallipoli Peninsula in Ottoman Turkey, opening the land phase of the Gallipoli Campaign in World War I. The landing came after a failed Allied naval attack on the Dardanelles Straits on March 18th, 1915, which convinced commanders that shore defenses had to be taken by infantry. General Sir Ian Hamilton split the force into two main groups: the British 29th Division landed at Cape Helles on the southern tip of the peninsula, while the Australian and New Zealand Army Corps (ANZAC) landed north of Gaba Tepe at what became known as Anzac Cove. The goal was to push through the Dardanelles, capture Constantinople (now Istanbul), and knock the Ottoman Empire out of the war.
United States Joins World War I
When World War I began in 1914, Woodrow Wilson was the President of the United States. The neutrality of the United States in World War I was a major factor of Wilson’s first term as president. In fact, when he ran for re-election in 1916, he campaigned on the idea that he kept the country out of the fighting of World War I.​
​In 1917, the German Empire again began carrying out unrestricted submarine warfareA naval strategy where submarines attack any ships, including civilian ones, without warning. and was one of the main reasons that the United States eventually joined the war effort on the side of the Allied Powers. In fact, in February of 1917, it was discovered that Germany had been in contact with Mexico in hopes of igniting a conflict between Mexico and the United States. This was known as the Zimmermann Telegram, and when combined with Germany’s submarine warfare, it pushed Wilson to eventually declare war against Germany.
Following their entry into World War I, the United States quickly mobilized forces and readied them for battle on the Western Front in Europe. The arrival of the American forces to World War I was significant for the Allied Powers. For instance, by 1917, the British and French armies had been bogged down in the trenches of Northern France for the previous 3 years. They were suffering from the terrible conditions of the trenches and stuck in a stalemate with the German Army. As such, the arrival of American forces helped create a shift in the balance of power in favor of the Allied Powers. This shift eventually led to the end of World War I.
FactsthatCrunchHome Front of World War I
​The home front was a major aspect of World War I and played a key role in the history and significance of the war. The home front involved the societies for the different nations involved and the issues faced by the citizens who did not fight in the front lines of World War I. For instance, all of the countries involved in World War I were impacted on the home front in different ways. With that said, there were some similar issues faced by all of the nations involved.
​First, civilians suffered due to battles that affected cities and towns across the battlefields of Europe. For example, the trenches of the Western Front stretched through areas across Belgium and northeastern France, including through farms, towns and cities. This displaced numerous people in the region and led to casualties among the civilian populations of Europe. Another issue for civilian populations was the lack of resources. Each country prioritized its resources for the front-line soldiers, which meant that people on the home front sometimes suffered.
​Other impacts on the home fronts of World War I included: the changing role of women, the use of propaganda and the use of conscriptionA government policy requiring citizens to serve in the military by law. (mandatory military service).
FactsthatCrunchEnd of World War I
​The end of World War I occurred due to a variety of factors. As stated above, the arrival of the United States on the Western Front was a major factor. American soldiers, alongside other Allied troops (Britain, France, Canada, Australia, New Zealand, etc.) were able to push forward during the Hundred Days Offensive and force the German Army back from the trenches of northern France.
Combined with the push of the Allied forces was the downfall of the Central Powers as a military force in Europe. In fact, the other Central Powers (Austria-Hungary, Bulgaria and the Ottoman Empire) all pulled their forces from the war before Germany. This effectively left Germany as the final Central Power fighting against the Allied Powers on its own. This was, obviously, an unsustainable situation for Germany and resulted in the German government seeking an armisticeA formal agreement between enemies to stop fighting, ending active combat., which occurred on November 11th, 1918 at 11am. With this World War I was over.
FactsthatCrunchThe fighting in World War I stopped at 11 a.m. on November 11th, 1918, the eleventh hour of the eleventh day of the eleventh month.
Germany signed the armistice in a railway carriage near Compiègne, France, at about 5 a.m. that morning, but the ceasefire did not take effect until 11 a.m. Soldiers kept fighting, and dying, in the hours between. November 11th is still remembered as Armistice Day, Remembrance Day and Veterans Day.
Treaty of Versailles
While World War I came to an end on November 11th, 1918 with the signing of the armistice, it was the Treaty of Versailles that truly ended the war. The treaty was a document that ended the war between the Allied Powers (Britain, France and the United States) and the Central Powers (Germany and Austria-Hungary). The Treaty of Versailles was signed on June 28th, 1919 in the Hall of Mirrors at the Palace of Versailles in France.
​The three main politicians that participated in the signing of the Treaty of Versailles were: Woodrow Wilson of the United States, David Lloyd George of Britain and Georges Clemenceau of France. Each leader had their own view on how to handle the end of World War I and to what degree Germany should be punished. In general, both Britain and France wanted to punish Germany while Woodrow Wilson proposed a different path with his famous ‘Fourteen Points’.
In the end, the wishes of Britain and France won out, and the Treaty of Versailles focused on punishing Germany with a variety of clauses. This was a significant event as it set the stage for the rise of Adolf Hitler and the eventual events of World War II. In fact, historians consider the Treaty of Versailles to be a cause of World War II.
FactsthatCrunchThe three main Allied leaders at the Paris Peace Conference in 1919 each wanted something different from the Treaty of Versailles.
Explore World War I · 1914 – 1918
Keep exploring World War I with these History Crunch resources.
Key Vocabulary
Militarism
Imperialism
Nationalism
Stalemate
Unrestricted submarine warfare
Armistice
Conscription
Frequently Asked Questions
What were the main causes of World War I?
World War I had four long-term causes known by the letters M.A.I.N., which stand for militarism, alliances, imperialism, and nationalism. These forces built up tension across Europe for years before 1914. A short-term cause, the assassination of Archduke Franz Ferdinand, then set the war in motion. Together these causes pulled the major powers into a global conflict.
Who assassinated Franz Ferdinand and why?
A Serbian nationalist named Gavrilo Princip shot Franz Ferdinand and his wife Sophie on June 28th, 1914 in Sarajevo. Princip was only nineteen and belonged to Young Bosnia, a group armed by a secret society called the Black Hand. The group opposed Austro-Hungarian power in the Balkans and wanted Serbia to be free of its influence. The killing triggered the July Crisis, and war began about a month later.
What was trench warfare like in World War I?
Trench warfare involved two armies digging long ditches in the ground that faced each other. Soldiers used the trenches to hide from enemy gunfire while they waited to attack “over the top.” This style of fighting led to long stalemates where neither side gained much ground. New weapons like machine guns, poison gas, tanks, and artillery caused huge numbers of deaths.
Why did the United States join World War I?
The United States joined in 1917 mainly because Germany used unrestricted submarine warfare against ships. Another reason was the Zimmermann Telegram, in which Germany tried to push Mexico into war with the United States. These two events led President Woodrow Wilson to declare war on Germany. American troops then helped shift the balance of power toward the Allied Powers.
How did World War I end?
The fighting stopped with an armistice signed on November 11th, 1918 at 11am. Allied forces had pushed the German Army back during the Hundred Days Offensive, and the other Central Powers had already quit. The Treaty of Versailles then officially ended the war on June 28th, 1919. That treaty punished Germany harshly, which many historians see as a cause of World War II.
Cite This Article
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MLA: Beck, Elias. “World War I: A Detailed Overview.” HistoryCrunch, 28 September 2026, https://historycrunch.com/world-war-i-overview/.
APA: Beck, E. (2026). World War I: A Detailed Overview. HistoryCrunch. https://historycrunch.com/world-war-i-overview/
Chicago: Beck, Elias. “World War I: A Detailed Overview.” HistoryCrunch. September 28, 2026. https://historycrunch.com/world-war-i-overview/
Sources
- Imperial War Museum
- Hew Strachan, The First World War.
- Margaret MacMillan, The War That Ended Peace.
