You also should give "History Line 1914-1918" a try (US-Title: "Great War 1914-1918"). It's turn-based, multiplayer-capable (two at the same time at one PC), the maps are designed with a hexagonal grid (like in "Panzer General").
It's a very old game, released by BlueByte (SSI in the USA) in 1992/1993, but definitely worth a look if you manage to obtain a copy
Wiki:
http://en.wikipedia.org/wiki/History_Line:_1914-1918