Before there was ASL, there was Squad Leader and its expansions, published by Avalon Hill. Great games in their own right even though they have been overshadowed by their Advanced counterparts.
Mapboard 1 : Squad Leader
Mapboard 2 : Squad Leader
Mapboard 3 : Squad Leader
Mapboard 4 : Squad Leader
Mapboard 5 : Cross of Iron
Mapboard 6 : Crescendo of Doom
Mapboard 7 : Crescendo of Doom
Mapboard 8 : GI: Anvil of Victory
Mapboard 12 : GI: Anvil of Victory
Mapboard 13 : GI: Anvil of Victory
Mapboard 14 : GI: Anvil of Victory
Mapboard 15 : GI: Anvil of Victory
(source: ASL Mapboard Publication List)
Advanced rules and modules: Advanced Squad Leader.
Variant rules: Retro: Tactical WWII Wargame Variant Rules.