In 1908, Austria - Hungary occupied Bosnia.

Inside of Bosnia, lived a lot of Bosnians, Coatians, and Serbians.

One Serbian, named Gavrilo Princip, apart of the Black Hand group, killed archduke of Austria, Franz Ferdinand on June 28th, 1914. 

In response, Austria and Germany declared war on Serbia. Serbia's allies Russia and Montenegro, declared war, too.

Russia's ally, France, also joined the war, because it wanted the Alsace-Lorraine which it had recently loss to Germany.

The Germans used a plan called the Schlieffen Plan go through Belgium on  August 4th, 1914 to get to France because France had a lot of forts bordering Germany.

After the invasion of Belgium, the UK didn't like that Germany was attacking neutral countries and entered the war. 

Austria tried to attack Serbia, but got forced back at the Battle of Cer which took place August 15 to 24 1914.

Soon, the Ottoman Empire joined in October of 1914, when some ships attacked Crimea because Russia helped a lot of rebellions get independence.  

The Ottomans tried to attack Russia in the Caucasus, but froze in the cold.

In 1915, the Ottomans also made a campaign in Egypt, but T.E Lawrence, a British officer, and some Hejaz soldiers kept blowing up trains and messing with the Ottomans plans.

On February 19, 1915, the Ottomans had its first victory when British, Australian, and New Zealander forces attacked the Gallipoli Peninsula in a failed naval invasion.

In May, Italy - who had an alliance with Germany and Austria - joined Serbia's side, by now known as the Entente, because of promised land and tense relations with Austria.

That same year another joined the Entente, Japan in August. Japan was building an empire and was happy to take German colonies in the Pacific.

Later on October 14th, Bulgaria joined the war. Bulgaria joined because it lost the Second Balkan War to Serbia.

Bulgaria helped Austria defeat Serbia and Montenegro and chased their armies hiding in Albania.

By 1916, the war was at a stalemate. On the Western Front, trenches ran from Belgium, through France, and stopped north of Switzerland.

General Brusilov, a Russian General, had some progress pushing German forces out of Russia, but got stopped.