The alliance system was one of the main causes of World War One. The alliance system was made up of two groups, the Central Powers (Germany, Austria- Hungary, Italy (1914), and Turkey). Germany, Austria-Hungary, and Italy formed the Triple Alliance. In 1882, they signed a document that promised they would give each other military support in case of a war. The second group was the Allied powers (Russia, France, Great Britain, and the United States).