Causes of WWI
A.  Industrialism led to increased economic competition among European nations, and with China, Japan, the United States, and the Latin American countries. The main competition was between Great Britain, the first to industrialize, and the new united Germany, who began industrializing rapidly after 1870.

B.  Militarism is a glorification of armed strength or weapon capability and a belief in military battle as the only true solution to international conflict.  The result of militarism is an arms race.  Countries find themselves locked in a vicious circle of weapons development.  There is a constant need for new and better weapons  which in turn produces a need for even better weapons on the part of neighboring nations.
 Militarism and an arms race make for a very profitable business for new industrialists (capitalists) who manufacture weapons.  Peace is not profitable for them, so the weapons manufacturers often fuel the arms race by convincing their governments that the threat from other countries is real.  Sometimes arms traders and war profiteers begin selling to any nation that will pay the price.
 The result of militarism and industrialism is huge stockpiles of weapons.  It is more likely that wars, big or small, will start if a country or group of allies have the weapons and trained armies ready to go to war.

 C.  Imperialism is another form of competition between nations as they compete to control natural resources and peoples in other parts of the world.  Great Britain had the greatest number of colonies, protectorates, and spheres of influence around the globe, because her navy continued to grow and control the sea routes.  Germany, as a new unified nation, felt it had to catch up with Britain and France, especially in Africa and to a lesser extent in China.
All European countries justified imperialism for the following reasons:
1.  economic gain via exploitation of natural resources and peoples.
2. political strength in order to bolster their position in the European balance of power.
3.  military/strategic positioning for controlling/defending colonies overseas.
4.  religious fervor of missionaries wanting to bring Christianity to other parts of the world.

D. Nationalism is another cause of WWI.  An explosive kind of nationalism existed in the Balkans (Serbia, Greece, Romania, Bulgaria, Montenegro, Albania, Bosnia, and Herzegovina) and was based on the Slavic nationalism encouraged by Russia to bring all of the Slavic peoples under its influence.  Serbia pushed for the creation of one "Slavic" state that it would dominate.  Austria-Hungary was opposed to giving up territory in which Slavs lived.

Pan-Slavism - A philosophy promoted by Russian leaders to encourage Slavic peoples in the Balkans to look to Russia for religious (Eastern Orthodox), cultural (Slavic languages), and political guidance.  The Russians were also interested in promoting Balkan resistance and rebellion against the Ottomans.

Russo-Ottoman War (1877-78)  Supposedly enraged by Ottoman atrocities against Slavic peoples, Russia declared war and defeated the Sultan's forces.  Russia forced upon the Ottoman empire a peace treaty that gave Russia great influence in the Balkans.  England and Austria-Hungary denounced this treaty and demanded a Balkan settlement by international conference.  Under threat of war, Russia agreed to a conference in Berlin.
 
1878 Congress of Berlin.  By this conference, Ottoman empire
 a)  allowed Austria-Hungary to occupy the southern Slavic provinces
  of Bosnia and Herzegovina
 b)  allowed England to occupy the Mediterranean island of Cyprus
 c)  granted independence to Serbia, Montenegro, and Rumania
 d)  granted Bulgaria self-government within the Ottoman empire
 e)  agreed that Russia receive certain Balkan territory

1882  Ottoman empire also recognized England's domination over Egypt.

E.  Alliances
Germany -- Bismarck, fearing that France might attempt some type of revenge for its humiliating defeat during the Franco-Prussian War and its loss of the valuable coal region of Alsace-Lorraine, wanted to keep France isolated from the rest of Europe.  Therefore, he formed the following alliances against France:
 1879:  Dual Alliance with Austria-Hungary as a mutual defense pact
 1881:  Three Emperor's League with Russia and Austria-Hungary
 1882:  Triple Alliance with Austria-Hungary and Italy
 1887:  Reinsurance Treaty with Russia.
This agreement excluded Austria-Hungary which Russia hated because of its control of Slavic territory and peoples.  This treaty stated that Russia and Germany would remain neutral if war broke out.  All of these treaties were in danger when Kaiser Wilhelm II came to power and dismissed Bismarck.

New Alliances in Post-Bismarck Europe
 Meanwhile, France was still upset about the loss of Alsace and Lorraine and fearful of Germany's growing industrial and military power.  When Kaiser Wilhelm II succeeded his grandfather, France moved quickly to negotiate an agreement with Russia.  Russia agreed to form an alliance with France in exchange for financial loans.  Russia was very poor and barely industrialized despite Peter the Great's and Catherine the  Great's efforts to modernize the country.  In addition, all of the wars against the Ottoman Empire took their toll.  In 1894, France and Russia allied.  Germany now faced one of its greatest fears, the possibility that if war did occur it could be a two-front war.  (In reaction to this concern, German military planners worked hard to devise methods of avoiding a two-front war.  When WWI finally begins, Germany will try to use the Schlieffen Plan to make a quick and decisive attack against France by going through neutral Belgium.)
 France also came to an agreement with Britain in 1904, forming the Entente Cordiale, which just said the two countries would be friendly.  In 1907, Russia joined them in the Triple Entente.  Although Russia and Britain were far from close friends, they recognized the value of a mutual agreement in the face of a possible German aggression (balance of power diplomacy).  Once Russia lost the Russo-Japanese War, Britain was willing to ally, at least distantly with Russia.   Britain was also worried about increasing German naval power and did not want to lose her place as the number one naval strength in Europe.
 At first, the new alliances seemed to be a good idea.  The feeling of security each  major power got from allying with another strong country, however, can also be seen as making them more comfortable to make a fuss about minor issues.  With an ally behind them, some countries felt secure in pushing their enemies around.  Smaller nations especially might press more for their goals if they know they have "big friends" who will come to their defense.  Some historians say that the alliance system in Europe was another factor that led them into World War I.
 
 The Crises Before the War
The competition among European countries was not confined to military action in northern Europe.  There were two major areas of tension:  Africa and the Balkans.  The rules for colonizing Africa were set at the 1885 Berlin Conference, but it took until 1904 for France and England to agree on areas of influence for each in Africa.  The Balkans were slowly becoming independent from the Ottoman Empire as its power weakened.  Austria-Hungary and Russia were competing to influence or rule the Balkan countries as they separated from the Ottomans.
 

MOROCCO
France was very interested in controlling North Africa to broaden its control over the Mediterranean.  England already had Egypt and influence over the Arabian peninsula as well as India, so it could tolerate expanded power by the French.  Germany, a new player at colonization, was jealous of France's moves to take Morocco and staged a confrontation that could have been the start of World War I.

By 1905 France made it clear to its European neighbors that it wanted to control Morocco.  Italy and then Britain agreed, because they had French approval for their own colonies in Libya and Egypt respectively.  France then got Spanish agreement based  on splitting off part of Moroccan territory across from the Gibraltar Straits for Spain.  The German chancellor, Bulow, felt threatened by French expansion and got Kaiser, Wilhelm II, to land at Tangier and salute the Sultan of Morocco as an "independent" ruler in whose lands "all foreign nations" would enjoy equal rights.   After some tense days among all of the European players, the French foreign minister, Delcassé resigned and France submitted the issue to an international congress.  The congress met at Algeciras in Spain in 1906.  Britain and Italy backed France.  They allowed France and Spain to "instruct" and staff a Moroccan police force and oversee "reforms" for Morocco.  The story wasn't over though.  In 1911, France sent an army to Fez to help restore order during some civil unrest.  Germany then sent a warship "to protect its mining operations" and, obviously, to threaten France.  England let Germany know that it would support  France, and Russia said the same, though it could not do much.  Russia was still recovering from its defeat in the 1905 Russo-Japanese War and trying to deal with its own revolutions.  Faced with the combined forces of France and England, Germany backed down but not without demanding an "open door" to business in Morocco and French colonies in the Congo, an equatorial region of Africa.  The end result was that Germany looked like a bully, and France and England got to be closer allies.
 
THE BALKANS
The Balkans are the areas of Bulgaria, Rumania, Greece, Serbia,  and Montenegro.  Serbia also wanted Bosnia and Herzegovina to join them in a Pan-Slavic movement, but the Austro-Hungarian empire annexed Bosnia when the Ottomans were busy putting down an internal revolution by the Young Turks.  Even though Austria-Hungary had been administering the territory since the Treaty of Berlin was signed in 1878, Serbia was really angry at the Austro-Hungarian empire for thwarting its plan to take Bosnia for access to the Adriatic Sea.  Serbia's only ally at the point, Russia, was too weak from losing the Russo-Japanese War to help it, and Germany came in on Austria's side.  Militant nationalist groups formed in Serbia, and Germany's military leaders started to feel encircled:  France in the west and Russia in the east.  In 1912-13, the Balkan countries formed the Balkan League and went to war against the Ottomans.  They won, because the Ottoman empire could not inspire non-Turkish peoples with the modern nationalism forming among the Young Turks; it was too far behind in its industrialization and militarism.

Like Morocco, the Balkans were an area contested by many countries in Europe.  By 1912, France and England furthered the Entente Cordiale by coming to a military understanding.  Britain would protect the English Channel and North Sea.  France would concentrate on keeping the Mediterrean open to both countries.

The Last Crisis:  The Assassination of the ArchDuke Ferdinand
On June 28, 1914 the ArchDuke of Austria-Hungary, Francis Ferdinand, was assassinated in Sarajevo, Bosnia.  Francis Ferdinand was heir to the throne of the Austro-Hungarian empire and wanted to reform the restrictive policies against Slavs in the empire.   Militant Slavic nationalists in Serbia did not like Francis Ferdinand's ideas about reform.  They needed Slavs to be upset and needing Serbian help to free themselves from Austria-Hungary.  One militant group called the Black Hand trained the assassin, Gavrilo Princip, who shot the ArchDuke and his wife while they were going through the streets of Sarajevo in an open car.  The assassination started the chain of decisions that led to the military battles of World War I.

Austria-Hungary's response to the assassination was an ultimatum to Serbia:  accept the following list of demands or suffer the consequence of war.

THE ULTIMATUM
1.  Serbia would ban from its schools any teachers or books that did not support the empire of Austria-Hungary.
2.  Serbia would condemn any anti-Austro-Hungarian propaganda.
3.  Serbia would dismiss any officials who promoted any anti-Austro-Hungarian propaganda.
4.  Austro-Hungarian judges would preside over the trial of those involved in the Sarajevo assassination.

Serbia accepted all of the demands but the last one.  Austria-Hungary refused to back off of its ultimatum, so it declared war on July  28, 1914.  What happened during that month in the summer of 1914?

Austria-Hungary contacted its ally, Germany, who said that Austria-Hungary should hold to its ultimatum.  Austria-Hungary interpreted Germany's response to mean that Germany would back Austria-Hungary all the way to war.

Serbia contacted its ally, Russia, who said that Serbia should also stand firm.  Russia's ally France promised to support any action Russia took in the Balkans.

CHRONOLOGY OF THE START OF WWI
1.  July 28, 1914:  Austria-Hungary declared war on Serbia.

2.  Russia mobilized forces to support Serbia along the Austro-Hungarian and German borders.

3.  Germany ordered Russia to cancel mobilization.

4.  France promises support to Russia.

5.  August 1, 1914:  Germany declared war on Russia.

6.  August 3, 1914:  Germany declared war on France.

7.  Germany moves to invades neutral Belgium, using the Schlieffen Plan to avoid the heavily fortified border with France by going through Belgium.  Germany wanted to quickly take over France, so it doesn't have to fight France and Russia at the same time.  England warns  Germany not to violate Belgium neutrality.

8.  Germany invaded Belgium on August 4, 1914.  England declared war on Germany.

9.  Italy remained neutral, claiming that the Triple Alliance didn't count if Austria-Hungary and Germany were invading, not being invaded. Italy also decided to stick to its secret alliance with France to get some of the Austria-Hungarian territory in northern Italy if the Triple Alliance lost.

10.  Turkey joined the Central Powers (Germany, Austria-Hungary) in November 1914 to fight its old enemy Russia.