Alliances are when countries team up against another country.  When an alliance is signed those countries become known as allies. European countries divided into two armed hostile camps. One was the Triple Alliance which includes Italy, Austria-Hungary and Germany. The Triple Entente which includes great Britain, France and Russia. The Triple Alliance would become known as the Central Powers and went on to include the Ottoman Empire and Bulgaria.

A lot of alliances had been signed by countries between the years of 1879 and 1914. It was important for this to happen because it meant that some countries has no option but to declare war if one of their allies declared war first. It created a lot of competition between the rival countries possibly even the allies themselves because they all wanted to be the most powerful country in their group. This increased the tension between everyone and strengthened each side for the war.