Of course the Great War wasn't entirely fought by soldiers sitting in trenches....

The trench system was a defensive fortification. The vast bulk of the war was also NOT spent in large set piece battles. Troops occupied trenches. Occaisionally, small scale raids were conducted, usually at night. Shellfire was swapped regularly, as were sniper bullets. Trenches were shelled....destroyed...repaired. And so it went on. Sometimes, if a perticularly useful shell-hole appeared, sappers would dig trenches out to it, to occupy it as a strongpoint. If you have ever seen some of the 'trench raiders' wepons...NASTY. Clubs wrapped in barbed-wire, axes, knives. Trench raids were a common tactic to get prisoners, information, and to strike fear in the enemy.

Then, every now and again, Field Marshal Haig would get the urge to re-site his drinks cabinet a few feet closer to Berlin, and a 'Big Push' would happen. Massive bombardments with millions of shells fired ( and about 2/3rds probably actually going bang... ) in abortive attempts to cut the wire. German WW1 wire was wicked stuff... ANd their dugouts were so deep the shells seldom damaged them. Then, over the top. A slow walk forward through bullets and counter-fire. If enough men were still alive when you got to the enemy trench, you might take it. If the reserves got up before the counter-attack, you might even hold it.

The big battles like Somme, Verdun, Ypres ( 1,2 and 3) were this sort of affair. There actually weren't that many 'big' battles. The death tolls in such offensives took a long time to recover from.

On the Russian front, though, the terrain was VERY different. IT was a lot more rugged, and far less suited to defending trenches. The terrain here ranged from mopuntainous regions through to swamps and marshland. Not places you could..or would...dig in!

Realistically...you would be foolish in the exteme to try and re-create this picture in it's entirety. Far better to take the START point of WW1, and use it's military advances to guide the development of the thing. You will have a lot of problems trying to follow either the economic or political background to WW1. Princip's assasination effort was both the catalyst and the excuse for war, in the light of a very complex political mess. The RTW AI is far too simplistic to do a good job of following the events.

The other area you are going to have BIG problems is with enemy battlefield AI. It has a rudimentary understanding of the basic weapon types. It thinks in terms of swords and spears, and will only really try to close into close quarters. If you attack it across no-mans land at the charge..it will counter charge. That would NEVER happen. There is also the archers tendancy to 'retreat' and keep firing. Again...in trench warfare, you would hold your ground and stay where the cover was best. I haven't seen any mods that really change the AI behaviour in these respects....