Germany entered into World War I on August 1, 1914, when it declared war on Russia. In accordance with its war plan, it ignored Russia and moved first against France–declaring war on August 3 and sending its main armies through Belgium to attack Paris from the north. The German invasion of Belgium caused Britain to declare war on Germany on August 4. Most of the main parties were now at war. In October 1914, Turkey joined the war on Germany's side, becoming part of the Central Powers. Italy, which was allied with Germany and Austria-Hungary before World War I, was neutral in 1914 before switching to the Allied side in May 1915.