The Battle of the Aisnes is the first battle that showcases trench warfare in the Great War.  Beginning on September 14, 1914, this battle between the British and the Germans was separated by a distance of 30 meters and each trench stretched out 2 kilometers in either direction.  This is where the battle style is seen making the drastic change from deadly short offenses to long defense-oriented battles.  Each side dug into the muddy ground near the river and since this was the earliest form of trench warfare they did not have them dug very deep and they were not connected via communication trenches.  However, this battle set the baseline for further trench developments in the war.