World War I started in summer of 1914 as apolitical power play in Europe. Russian and Austria-Hungary competed for control of Balkan region. Many Serbians wanted to unite all Slavs into a one country, so Austria-Hungary started to worry for the Pan-Slavic movement and they annexed Bosnia-Herzegovina. This angered many Serbians, as they wanted to be in control of Bosnia. Thus, on June 28 1914, Serbians assassinated the heir of Austro-Hungarians throne. As a result, Austria-Hungary declared war on Serbia on 28th of July. Russia, which was an ally to Serbia, came to support Serbians in the war. Germany, an ally to Austria-Hungary and Italy, joined the fighting in Balkans, declaring war on the Russians on August 1st 1914. Germany attacked neutral Belgium two days after they declared war on the Russians, so they can get closer to the France. Great Britain started to worry about the entrance of Germans into the war as Great Britain had an alliance with France and Russia, so British entered the war on August 4th on the side of Russia and France and they became knows as Allied Powers. Germany, Austria-Hungary and Turkey were known as Central Power.
President of the U.S, Woodrow Wilson declared American neutrality in 1914, because he believe that it is a European war and America should stay out of their problems. However, U.S. was heavily trading with Allied countries, especially with England, rather that central Europe. In fact, the trade with Western Europe more that tripled, while trade with central Europe decreased by almost 90%. Many Americans believed that U.S. should spend money on social programs rather that war actions, so they were against the war. However many Americans held anti-German attitude, as Germany marched to the neutral Belgium. In addition, German use of U-boats, which sometimes attacked Americans ships without warning, angered many Americans. Sinking of British liner Lusitania had increased anti-German