Beginning on August 14, 1914 and ending with the armistice of December 6, 1917 that effectively ended World War 1, it was a far more fluid and mobile, unlike that of the trenches of the western front. This allowed great gains by Germany during the first years of the war, before the Constantinople Campaign reopened supply lines from the western allies to Russia, as well as the entrance of both Romania and Bulgaria (and to an extent Greece), allowed the entente to return to the offensive with massive breakthroughs against Austria-Hungary (as well as small breakthroughs in the German lines) in 1916 and 1917.