World War I was a conflict that began in 1914 and ended in 1918. It involved many countries in the world. This is why it is called a world war. On one side, the main countries were Great Britain, France, Italy, the United States and the Soviet Union. This side was called the Allies or the Allied Powers. The United States didn’t join the war until 1917, and the Soviet Union pulled out of the war in late 1917. On the other side were countries that were called the Central Powers. These countries included the empire of Austria-Hungry, the Ottoman Empire, Bulgaria, and Germany. The main countries that won in World War I were France, Great Britain, Italy, and the United States. Other countries that helped the Allies were also considered victorious. This does not include the Soviet Union because they pulled out of the war in November 1917. World War I ended on November 11, 1918 at 11:00 AM. This is when we celebrate Veterans Day.