A temporary local cease-fire to allow for the collection of wounded from no-man's land was uncommon but not at all unheard of. In every account I have read, these were initiated by an officer (a company officer or the battalion medical officer) climbing out of the trench holding a white flag, often accompanied by one or two more men also holding white flags, and walking forward to a half-way point in the hope that an officer from the opposing side would come forward to discuss the possibility and terms of a cease-fire.

The level of bravery and compassion that this took is truly humbling. White flags were generally respected on the Western Front (even if the opposing side flatly refused to come out and speak and warning shots were fired to drive them back), but a man doing this was exposing himself to immense danger. On a 1000 yard battalion front, there would be approximately 46 snipers and observers at any one time (5 pairs of specialists from battalion, and around 36 men from the two companies in the line), plus patrols, sentries, independent machine gun teams and artillery observers who could call in rapid pre-registered shellfire from the field gun and trench mortar batteries by telephone - he would be taking an enormous leap of faith in assuming that not a single one of these men was jumpy, traumatised or vengeful enough to fire on him.

I don't want to give the impression that this was in any way common. It ran contrary to every imperative from brigade-level upwards. The British General Staff was stung and deeply concerned by the fraternisation of the 1914 Christmas truce and adamant that behaviour of that sort should not be encouraged. Aggression and fighting spirit was kept up by demands for trench raiding and patrol activity, and any sort of fraternisation firmly discouraged. If a cease-fire was agreed to, it would be strictly localised and prone to breaking down at any moment. There was really no way to coordinate a wide-scale truce and it would almost certainly meet with disapproval and rejection from higher-ups, so when they did occur it was company and battalion officers who brokered the deal and agreed conditions.

Most wounded men who found themselves trapped in no-man's land after a failed attack or patrol would succumb to their wounds or drag themselves back under cover of darkness. Their comrades and battalion medical staff would also make attempts to recover them at immense risk to themselves, usually at night as a daytime attempt would be suicidal. The citations for gallantry medals are filled with awards to men who risked their lives (or lost them) to bring in the wounded under fire.

If you'd like to learn more about this subject the go-to resource is Trench Warfare 1914-1918: The Live and Let Live System by Tony Ashworth. His study goes into enormous detail about the ways opposing troops would sometimes find ingenious ways to reduce the level of violence on their own small section of front line with an attitude of 'live and let live':

Unofficial truces called variously: ‘let sleeping dogs lie’; ‘mutual obligation element’; ‘mutual understanding’; ‘characteristic trench warfare, sort of take the thick with the thin, compromise, and be mighty glad to be alive’. The unofficial policy of ‘live and let live’ was the antithesis of the official ‘kill or be killed’. (Ashworth, p19)