1914/1918 main Battle Fronts. Timeline = 4th. Aug. 1914: Britain declares war on Germany 23rd. Aug. 1914: Germany invades France. 26th. Aug. 1914: Russian army defeated at Tannenburg & Masurian Lakes 6th. Sept. 1914: Battle of the Marne begins. 18th.Oct. 1914: 1st Battle of Ypres. 29th. Oct. 1914: Turkey enters war on Germany’s side. Trench warfare starts to dominate the Western Front.