The Central Powers consisted of Germany, Austria-Hungary, the Ottoman Empire and Bulgaria. The name Central Powers is derived from the location of these countries; all four were located between the Russian Empire in the east and France and the United Kingdom in the west. Germany and Austria-Hungary became allies on the 7 October 1879, and were joined later on (20 May 1882) by Italy, which intended to limit the alliance to defensive purposes only When World War I began, the petition made by Germany and Austria-Hungary for Italian intervention was rejected by the Italian Government on the grounds of these two countries declaring war on Serbia, rather than taking defensive action against it. Italy eventually entered World War I on May 23, 1915, but it fought against Germany and Austria-Hungary rather than with them. Following the outbreak of war in Europe during August 1914, the Ottoman Empire intervened at the end of October by taking action against Russia, resulting in declarations of war by the Triple Entente. Bulgaria, still resentful after its defeat in July 1913 at the hands of Serbia, Greece, Romania and the Ottoman Empire, was the last nation to enter the war against the Entente, invading Serbia in conjunction with German and Austro-Hungarian forces in October 1915. During the years 1917 and 1918, the Finns under C.G.E. Mannerheim and the Ukrainian and Lithuanian nationalists fought Russia for a common cause. The Ottoman Empire also had its own allies in Azerbaijan and the Mountainous Republic of the Northern Caucasus. The three nations fought alongside each other under the Army of Islam in the Battle of Baku. Bulgaria signed an armistice with the Allies on 29 September 1918, following a successful Allied advance in Macedonia. The Ottoman Empire followed suit on 30 October 1918 in the face of British and Arab gains in Palestine and Syria. Austria and Hungary concluded ceasefires separately during the first week of November following the disintegration of the Habsburg Empire, and Germany signed the armistice ending the war on the morning of 11 November 1918 after the Allied Hundred Days Offensive, a succession of advances by New Zealand, Australian, Canadian, Belgian, British, French and US forces in north-eastern France and Belgium.