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 warfare
At various times during the war—particularly early on—official truces were organised so that the wounded could be recovered from no man's land and the dead could be buried. Generally, senior commands disapproved of any slackening of the offensive for humanitarian reasons and so ordered their troops not to permit enemy stretcher-bearers to operate in no man's land. However, this order was almost invariably ignored by the soldiers in the trenches, who knew that it was to the mutual benefit of the fighting men of both sides to allow the wounded to be retrieved. So, as soon as hostilities ceased, parties of stretcher bearers, marked with Red Cross flags, would go out to recover the wounded, sometimes swapping enemy wounded for their own.