Andy Watkins offers a set of relatively simple Vietnam War rules.
The Shellshock Combat System is a comprehensive set of free wargames rules for WWII, Modern and Science Fiction combat. Designed for micro scale (1/285), it features three “levels of play”: basic, advanced and “blitzkrieg” (fast play).
Able Archer is a set of free wargames rules for 1/300 scale modern combat.
The author writes:
Able Archer is wargaming system, which will put players into role of company or battalion commanders durning fictional conflict in 1983. You will assume command of NATO or WARPAC ground forces. You will lead tanks,infantry but even artillery or airforces. You will be fighting in conflict that was greatest fear of every politican and commander durning Cold war. Can you defeat Soviets before they could reach the Rhine? Or will you lead final push towards the Paris as Soviet commander?
Able Archer unlike many games situated in Cold war gone hot scenário, is played in 1:1 scale. That means 1 vehicle represent one vehicle, base of infantry represents team and so on.
In smaller games you will lead companies, while in larger games you can command battalions or even regiment worth of troops.
Because Able Archer is aiming for wargaming Cold War Gone Hot scenário in central Europe you can command United States,Soviet,Czechoslovak, Polish,British,Dutch,West or East German battlegroups. You can play Able Archer storyline or even try something different like Fortress America (Soviet Invasion of USA)
Incoming is a set of free wargames rules for WWII, Post-War and Modern Combat. Fitting on just two pages, it represents warfare at the brigade and division level.
World War III is a set of free wargames rules for the period “1950 to armageddon.”