Green Miniatures offers a set of free wargames rules for game set during the Great War. The smallest unit in the game is a platoon.
Rules: WWI
OP14 Operational Level Wargame Rules 1914 – 1918
Op14 is a set of free wargames rules for operational level game set in the World War I. The game is designed for figures on 15mm frontage bases, played on a grid.
I Wish I Was In France East Africa WWI Rules
I Wish I Was In France is a set of free wargames rules for WWI era games set in East Africa.
The Great War Naval Rules
The Great War Naval Rules is a very comprehensive set of rules for WWI Naval warfare.
Raging Empires WWI Rules
Raging Empires is a set of free wargames rules for WWI actions.
The authors write:
The Raging Empires rule system has been developed by WW1 enthusiasts to create a fast flowing game which captures the feel and flavour of this fascinating conflict.
This draft version of the rules contains all the game mechanics necessary to re-fight historical battles in all theatres and phases of the First World War, from the war of movement of 1914 to the major battles of 1916. This will be extended to cover 1917-18 in the full set of Raging Empires due for Autumn release.
One A4 Quick Reference Sheet is sufficient to contain all the information necessary to play. The main rules need only be consulted when players are learning the rules, and occasionally thereafter, to clarify situations as they arise.
Raging Empires is designed to be used for very large battles as well as relatively small encounters. The precision of the movement system and the speed and efficiency of combat makes the game flows quickly and even a closely fought battle of a moderate size can be concluded within 2 hours.
The game is designed to be played on modular hex terrain which can accommodate a range of different terrain features, e.g. open ground, trenches, strong points, hills and slopes, rivers, woods, impenetrable terrain etc.