The way trenches were designed and built changed during the war. I found an excellent resource to be Paddy Griffith’s Osprey Fortress book “Fortifications of the Western Front”, but as the project continued I got almost as much use out of Peter Barton’s panorama books on the Somme and Passchendaele. I’d recommend all of them very highly.
Early war trenches could be little more than earthen lined trenches in the ground, narrow and sometimes even in straight lines. As the war dragged on, trench systems became more elaborate, with familiar crenellated lines, curved or zig-zagged communications trenches and deep bunkers. The German Siegfried Stellung, to which the Germans retreated in early 1917, appeared to be the ideal fixed fortifications for the time it was first brought into use. It featured several different defensive lines, introduced elements of flexible defence in depth and contained deep belts of defensive wire to channel and dislocate the anticipated Allied attacks.
Nevertheless, despite the immense efforts used by the German Army in its construction, the Siegfried Stellung failed in its key objective of preventing Allied advances in 1917 and 1918. Quite a number of books, in particular Jack Sheldon’s “The German Army at Cambrai” make the point that the elaborate defences of the Siegfried Stellung were problematic for the German army to defend and maintain almost as soon as they were brought into use in early 1917.
We wanted to try and loosely model the trench terrain on the Siegfried Stellung. We liked the idea of a game where the Germans were holding their main battle line against British attacks, being forced to balance the apparent wealth of defensive fortifications alongside the insufficient manpower of a battle-weary stellungsbatallion. But we also thought of the Siegfried Stellung as an inspiration for the terrain boards, not a blue print. We wanted to be able to use the terrain for a late war British, Imperial, French or even American section of trench without feeling we were stretching credibility. And we also wanted the chance to later add to the initial terrain a number of boards featuring less precisely constructed trenches - such as series of trenches dug through a succession of shell craters in the heat of a battle.