Trench warfare
Trench warfare prevailed on the Western Front from late 1914 until the Germans launched their Spring Offensive on 21 March 1918. After the buildup of forces in 1915, the Western Front became a stalemated struggle between equals, to be decided by attrition. Frontal assaults, and their associated casualties, became inevitable because the continuous trench lines had no open flanks. Casualties of the defenders matched those of the attackers, as vast reserves were expended in costly counter-attacks or exposed to the attacker's massed artillery. There were periods in which rigid trench warfare broke down, such as during the Battle of the Somme, but the lines never moved very far. The war would be won by the side that was able to commit the last reserves to the Western Front.
Trench map
Partly in response to the evident deficiencies of such maps, the British Army put into use, starting in July 1915, the "Regular Series" trench map. These Regular Series maps, printed in Britain, did much to improve the situation (all 1:10,000 scale maps in this series, printed by the Geographical Section of the General Staff, bear the GSGS number 3062; 1:20,000 scale maps of this series bear the GSGS number 2742; maps of this series were almost invariably backed with linen, greatly improving their durability). Even after the Regular Series came into use in the Summer of 1915, however, local editions of maps, of different formats and printed at the front, remained in use, and did so throughout the war.