Too Fat Lardies Great War skirmish rules.

From the Publisher:

"The rules are designed for large skirmishes, from 30 to 100 figures a side, and are based around the actions of leaders in battle. As well as the main rules there is a supplementary section covering the organization and tactics of the Germans, French, British and US forces and details of WWI artillery tactics."

Through the Mud and the Blood is similar to the Lardies Sharp Practice and Troops, Weapons and Tactics skirmish rules. Emphasis is on leadership, not on technical differences between different bolt action rifles.