On June 28, 1914, Archduke Ferdinand, the heir to the Austria-Hungary throne, and his wife were assassinated by a Serbian national, plunging the world into war — the beginning of World War I.

While the assassination may have triggered the war, scholars are still debating the circumstances and events that caused the conflict.  Their theories as to the possible causes include:

  • The web of alliances that existed at the time, which prompted countries to defend their treaty partners.
  • A general belief that war was inevitable.
  • Military capitalism which would allow countries to potentially profit from war.
  • Empire building as countries fought over contested land.
  • A national Darwinism, or belief that the strongest country would survive.

In the end, over 9 million people died on the battlefield and the nature of war changed forever.

The Powers

The primary powers in the war were Germany, Austria-Hungary, Italy, and Turkey, which together formed the Central Alliance. Facing them were Britain, France, and Russia, also known as the Allies. Italy was originally allied with Germany and Austria-Hungary, but later changed sides.

European Tensions

The war started as events unfolded in the Balkan region of Europe. The Ottoman Empire was declining, and their influence over the Balkan countries was waning. The countries of Serbia, Russia, and Austria-Hungary all wanted a piece of the Ottoman pie.


How World War I Began: A Unit Study

In Austria-Hungary an underlying feeling existed that Serbian nationalism and Russian ambitions in the Balkans were causing the disintegration of the empire. Many believed that a limited war against Serbia could help hold the empire together. Historically speaking, the Second Balkan War of 1912-1913 occurred without major outside military involvement, so Austria-Hungary hoped for the same outcome.


Russia, on the other hand, believed that it needed to be the major power in the Slavic Baltic countries. If it did not actively play a part in the growing tensions and potential conflict, it believed that Serbia would rise as a power and possibly destabilize the Russian Empire. Russia believed that to maintain influence over Serbia it must support her in the future at all costs, having already failed to offer that support in the Balkan crisis of 1908. Therefore in 1912, Russia announced a military modernization program scheduled to be completed by 1916-1917. At the same time Serbia was being swept by a strong Slavic nationalist tide that threatened to destabilize the entire region.


Historic and ethnic allies with Austria-Hungary, Germany would naturally support its friends. Germany was being placed in the position where the Russian military was modernizing to their east, France was strengthening its military to the west, and Germany was in a naval race with Britain for supremacy at sea. Germany was being surrounded, and it was believed that when Russia completed their efforts, these Triple Entente members (the Allies) would be too strong to be defeated if a war occurred. Germany felt certain that war with Russia in the Balkans over territory was inevitable. Given these facts German opinion for the necessity of a preemptive military strike grew. This inevitability, combined with hopes of imperialist expansion and a growing tension as German nationalists pushed for war to whip up national support to counter the left-wing social democrat movement, helped create a formula for disaster.

All of these sweeping tensions resulted in the development and later modification of the Von Schlieffen plan, the German war plan to quickly neutralize the threat posed by the Triple Entente. The plan’s primary goal was to knock France out of the war in 6 weeks in order to bring all German resources against the Russian threat. German plans required a quick defeat of the Triple Entente members before Russia had the chance to complete their modernization program.

How World War I Began: A Unit Study


Britain was trying to maintain the European status quo while it grew its empire. Germany was threatening to change that balance. Both countries were looking at the potential to grab one another’s foreign assets in the event of war. Though not specifically stated, by signing treaties with Russia and France, Britain was essentially agreeing to go to war should either member be attacked. The British sentiment was to support their allies should war break out.


France was suffering from the same kind of left-right struggle as Germany. A war with Germany could increase nationalist sentiment and nullify the leftist-socialist movement.  In addition, the ruling class desired to recover the provinces of Alsace-Lorraine lost in the Franco-Prussian war of 1870-1871. French war plans were drawn focusing on regaining this land to revenge the loss.


Turkey hoped to hold on to the status it once held under the Ottoman Empire. Its world power and influence were decreasing as the central European countries grew in power. Eventually it would secretly negotiate a treaty with Germany and enter the war as one of the Central Power countries. It would declare a holy war to regain territory it had lost in the Balkans.  Turkey’s ambitions also included gaining the territories in Egypt and Cyprus being held by Britain.

United States

The United States initially maintained a neutral status, but was supplying Britain with much-needed resources during the first few years of the war. Eventually the Germans realized that their only hope for success in the war was to starve Britain and France of the necessities required to continue fighting. This led to unrestricted submarine warfare. Any ship in the German-designated war zone would be sunk if it were deemed to be carrying military supplies to aid the Allies in their efforts. Germany knew the blockade and unrestricted submarine policy would most likely bring the U.S. into the war, but hoped it would be too little too late. That policy, combined with an attempt to bring Mexico into the war against the United States, eventually led the U.S. to enter the war.

The control of worldwide foreign resources was another key tension at the time.  Germany and England were both involved in a serious power struggle in Africa to maintain control over diamonds and gold discovered in the late 1800s.  Further, the building of a so-called Berlin-Baghdad Railway was underway, which would give Germany access to Persian Gulf oil, and thereby threaten English control of the Persian Gulf area and India.

The War Timetable

With the Balkans being the tinder box, the events unfolded as follows:

  1. June 28, 1914: Archduke Ferdinand, the heir to the throne of the Austria-Hungary empire, and wife were assassinated by a Serbian nationalist in Sarajevo.
  2. July 28, 1914: Austria-Hungry, believing a war strike on Serbia could be kept regional, declared war on Serbia and Russia.
  3. July 29, 1914: Austria-Hungary invaded Serbia.
  4. August 1, 1914: Germany declared war on Russia.
  5. August 2, 1914: Germany invaded Luxembourg, setting the stage for the invasion of France.
  6. August 3, 1914: Germany declared war on France.
  7. August 4, 1914: Germany declared war on and invaded neutral Belgium, breaking a treaty signed by Prussia to keep Belgium neutral. Britain declared war on Germany and Austria-Hungary. Canada followed suit. U.S. declared policy of American neutrality.
  8. August 7, 1914: British forces landed in France.
  9. August17, 1914: Russia invaded East Prussia.
  10. October 29, 1914: Turkey entered the war on the side of the Central Powers.
  11. April 2, 1915: Germany declared a U-boat blockade of Britain. Any ship entering the blockade zone would be a fair target and would be sunk.
  12. April 26, 1915: France, Russia, Italy, and Britain concluded the secret Treaty of London setting the stage for Italy switching sides.
  13. May 23, 1915: Italy ignored Central Power Treaty and switched sides, declaring war on Austria-Hungary.
  14. July 15, 1915: Lusitania sunk by German U-boat killing 1198 civilians, and 128 Americans.
  15. September 20, 1916: Russia ended its Carpathia offensive, having inflicted significant damage against the troops of Austria-Hungary.
  16. December 12, 1916: Germany released a peace note suggesting a compromise peace.
  17. January 19, 1917: British cryptographers deciphered Zimmermann (German Foreign Minister) telegram sent to the German Minister to Mexico, offering United States territory to Mexico in return for joining the German cause.
  18. February 3, 1917: U.S. severed diplomatic relations with Germany.
  19. February 24, 1917: Zimmermann telegram passed from Britain to the U.S.
  20. March 1, 1917: Zimmermann telegram released to press by the U.S. State Department.
  21. March 15, 1917: Tsar Nicholas II of Russia abdicated as a result of the Russian Revolution.
  22. April 2, 1917: President Wilson delivered war address to Congress.
  23. April 6, 1917: U.S. declared war on Germany.
  24. June 26, 1917: First U.S. troops arrived in France.
  25. June 27, 1917: Greece entered war on the side of the Allies.
  26. July 11, 1917: Lenin overthrew the Russian government.
  27. December 3, 1917: German-Russian armistice signed.
  28. December 7, 1917: U.S. declared war on Austria-Hungary.
  29. March 3, 1918: A separate peace treaty was signed by Soviet Russia and the Central Powers (Germany, Austria-Hungary and Turkey) at Brest-Litovsk.
  30. September 29, 1918: Bulgaria concluded armistice negotiations with the Allies.
  31. October 30, 1918: Turkey concluded an armistice with the Allies.
  32. November 3, 1918: Austria-Hungary concluded an armistice with the Allies.
  33. November 7, 1918: Germany began negotiations for an armistice with the Allies.
  34. November 9, 1918: Kaiser Wilhelm abdicated.
  35. November 10, 1918: German republic founded as Kaiser Wilhelm II fled to Holland.
  36. November 11, 1918: Armistice Day in Europe. Fighting ceases at 11 a.m.  World War I ends.

Summary of Causes

Web of Alliances

The traditional theory as to what caused World War I is simply that the web of alliances that existed forced each partner into action.  There had been numerous treaties signed between the countries involved.  (See resources below for a complete list.)  As the timeline shows, events unrolled quickly, which would seem to indicate little to no hesitation on the part of the countries involved to stand with their allies.


There can be no doubt that most, if not all, of the countries involved believed to some degree that war was inevitable. Whether or not the general belief that there would be a war was the actual reason for war occurring at the time seems difficult to prove. In the end, this feeling of inevitability may have played some part in the final decisions as each country considered entering the war.

Military Capitalism

As nations ramped up their military strength, as the theory goes, capitalists wanted war to make a profit on their military wares.  As the nations increased their military might, military companies were increasing their profits.  However, should a war break out, many military companies would lose money, due to the loss of foreign military sales, as well as the significant danger from the loss of infrastructure (factories, stored goods, etc.). There would also be a significant risk of being on the losing side and the resulting unknown outcome.


Many theories exist as to the cause of the war, probably as many theories as there are students applying for advanced degrees in history studying World War I. Only a few were presented here. What does seem to stand out is that there were severe tensions, empires were collapsing or fading away, some degree of inevitability existed, and nationalism played a role. As scholars continue to debate the causes of World War I, examine the facts, review the order in which events unfolded, and follow the research.  What conclusions can you draw?

Further Investigation

The Causes of World War One
Brief introduction to the various strands that lead to the war.

World War 1 Timeline Index
Timeline dealing with the events making the “long fuse” that lead to World War I.  Helpful for understanding some of the causes mentioned above.

World War 1 Timeline
Very complete detailing of events.

Assassination of Archduke Ferdinand, 1914
Eyewitness to History account.   (May not be suitable for young children.)

Deadly Alliances
An explanation of the alliances mentioned above that were in place which pulled otherwise neutral countries into the war.

WWI Firsts
As countries of the world built up their military arsenals there were many WWI firsts. Brief clip from the History Channel. (You may want to install an ad blocker before viewing.)

The Zimmermann Telegram
Original document mentioned in the above timeline.  From the National Archives.

President Wilson’s War Message to Congress
Referenced in timeline above, original text of message.

President Woodrow Wilson’s 14 Points
Why the United States of America entered World War I.

Woodrow Wilson
Biography from Whitehouse.gov.


World War I: Europe Plunges Into War
Animated map showing countries entering the conflict as events unfolded.

Campaign Atlas to the Great War
Maps showing the geographic changes as they occurred with world-wide events.  From Westpoint.

Document Analysis Worksheet
Worksheet to help analyze the Zimmermann Telegram from the National Archives.

Decoding a Message
Sample substitution code system, similar to the Zimmermann telegram, to translate.

Units & Lesson Plans

United States Entry Into World War I
Lesson plan for upper level students examining the reasons the U.S. entered World War I using primary source documents.

Missions in Modern History — Emphasis: World War I The World Divided
World War I section from a free unit study with a focus on missions.

Printables & Notebooking Pages

The Causes of World War I
Graphic organizer to help plot cause, nations involved and results.

World War I Notebooking Pages
Simple 3-page download for summing up from Practical Pages (scroll down).

How WWI Began Notebooking Pages
Simple pages for copywork, narrations, or wrapping up.

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