Some descriptions come from a text book. Please do not sue me.
The German states take Alsac and Lorrain from France during war
Germany sought an alliance with Austria-Hungary and Russia.
Germany created the Dual Alliance
The Dual Alliance became the Triple Alliance when Italy joined.
France found an ally in Russia when Germany failed to renew a treaty.
Franco-Russian Alliance agree to help each other if attacked by Germany.
Britain signed the Entente Cordiale with France.
Count Alfred von Schlieffen had developed Germany's basic plan.
Britain, France, and Russia linked up the Triple Entente.
Austria annexed Bosnia and Herzegovina, making many Serbs angry.
Serbia saw Austria as its biggest obstacle to its expansion.
The German fleet was trapped in its port; Britain prevented Germany from importing war material by maintaining a blockade.
South Africa took German South-west Africa. Australia took German New Guinea. Japan seized Germany's Pacific islands colonies and territory in China.
Archeduke Franx Ferdinand and Duchess Sophie are assassinated in Sarajevo, by Garvilo Princip.
Austria presented Serbia with an ultimatum.
Austria declared war.
Germany attacked France through neutral Belgium
Germany declared war on Russia.
Germany declared war on France
Belgian resistance delayed Germany's advance and helped French and British forces to halt the Germans in northern France.
Russian forces captured Armenia from Turkey
Italy withdrew from the Triple Alliance, and joined the Allies.
Soon after Rumania joined the Allies, Austrian and German troops overran the country.
Germany shipped arms to Irish rebels, unsuccessfully revolting against British rule in Ireland.
The United States of America joined the Allies
Russia's military was collapsing in the beginning of this year, and and the Revolution ended the country's involvement in the war.
Germany sent out U-boats to sink allied shipping. U-boats began to attack ships of neutral countries. The USA joined the Allies because of this.