How were they able to coordinate, plan, move supplies, and actually build complex trench systems while under constant enemy fire? Especially when a lot of the time the enemy was only a few hundred yards away.
I understand most of this probably happened in 1914, but there was still enough movement going on that new lines needed to be created.
Can anyone offer some insight or somewhere to learn exactly how the process would have been executed?
Thanks!
Mostly at night and with appalling numbers of casualties.
Field Entrenchments: Spadework for Riflemen by John Solano (first published in 1914, with updates throughout the war) is a superb resource and can be viewed in its entirety on-line thanks to archive.org. Have a look in particular at Chapter III (page 39) Entrenchment in the Presence of the Enemy. This gives a very detailed description of how a full trench line can be constructed and developed, starting off with shallow, hastily grubbed-out pits dug by individual riflemen while under fire.
A trench system would be incrementally developed and improved, day after day, with back-breaking labour by the infantry. In a 'loud' sector where enemy observation and fire was too intense to achieve much by day, working parties would move up from the support lines under cover of darkness and work through the night. Reliefs (one unit taking over responsibility for a front-line trench from another) and movement of supplies would also take place chiefly at night. Any movement of troops or wagons was liable to draw artillery fire, and choke-points such as communications trenches and crossroads just behind the lines were generally known and pre-registered by the enemy artillery, even if they were out of direct sight, and would come under random bombardment in the hope of catching a party on the move and disrupting their efforts. Working parties in the line (or in front of the line working on the wire) that drew attention to themselves because they made too much noise or were spotted when flares and illumination shells went up would be shelled and machine-gunned. Ultimately, the casualties that all of this inflicted simply had to be borne and the work carried on, as without improvement and supply a trench line was vulnerable to attack.
Trenches and strong points might also be taken from the enemy, rather than dug from scratch, and reversed, joined up and incorporated into the existing front line. This again would be achieved with enormous loss of life and hard, frantic, terrifying, physical work. I mentioned a bit about how trenches were raided, taken and reversed in an answer to this question:
What happened after a successful attack against an enemy trench in WWI?
It wasn't all like this, however. There were plenty of 'quiet' sectors where working parties from both sides would allow each other to go about their business unmolested, in a spirit of 'live and let live'. Rations and other supplies could be moved in daytime, and in some cases weapons fire was even ritualised so you would know exactly when to expect a handful of enemy shells to arrive, fired to satisfy the reports back to HQ rather than to inflict casualties. Trench Warfare 1914-1918: The Live and Let Live System by Tony Ashworth is an amazing study of this facet of the war and well worth a read.