Political map of Europe & the Mediterranean 26 April 1915 (Gallipoli Campaign): The Ottoman Turks had entered the War (World War I) on the side of Germany in October 1914, threatening the Suez Canal (First Suez Offensive) and the Persian oil wells. Even more critically, supply routes to Russia's major ports were now blocked (by the Germans in the north and the Turks in the south). In an attempt to force open the southern route (Dardanelles), the Allies landed at Gallipoli (Gallipoli Campaign) but were unable to break Turkish defenses.