The idea of simultanous turn based gaming is quite old, actually. In industrial age around 1800, it has surfaced as Kriegsspiel - german for wargame - and was used to train officers in the Prussian army. Also, the concept is well known in the board game community, with early game system titles like Diplomacy beeing released in 1959.

As for computerized versions of simultanous turn based system, the play by mail and then the play be email genre spawned many a game. Notable examples of more complex, large scale war-gaming that orginated in the 1980s and 1990s are STARWEB (by Rick Loomis, now remade as RSW-Game), Olympia (Shadow Island Games/Rich Skrenta), Galaxy and Atlantis (both by Russell Wallace) and Wolfpack Empire.

All of these games use a certain degree of abstraction when it comes to the simulation of the player unit's action in the game world - some of them tend to simulate more, while others are more on the abstract side of this. While these games represent very complex game systems that are not found anymore in todays strategy game shelves - mostly for market reasons and the problem of GUI - some of these games are still played by hard core strategy enthusiasts.

I advise to search for the games mentioned above to find out whether some instances are still running.

The idea of simultanous turn based gaming is quite old, actually. In industrial age around 1800, it has surfaced as Kriegsspiel - german for wargame - and was used to train officers in the Prussian army. Also, the concept is well known in the board game community, with early game system titles like Diplomacy beeing released in 1959.

As for computerized versions of simultanous turn based system, the play by mail and then the play be email genre spawned many a game. Notable examples of more complex, large scale war-gaming that orginated in the 1980s and 1990s are STARWEB (by Rick Loomis, now remade as RSW-Game), Olympia (Shadow Island Games/Rich Skrenta), Galaxy and Atlantis (both by Russell Wallace), Prometheus (Mathias Kettner) and Wolfpack Empire. Order cycles usally were about one week due to the high amount of game units and order complexity e.g. 200 units with 5-6 orders each. A modern representation of this kind of game system is the open source game Freeciv.

All of these games use a certain degree of abstraction when it comes to the simulation of the player unit's action in the game world - some of them tend to simulate more, while others are more on the abstract side of this. As such, some games do not feature fully simultanous game actions, while others try to emulate this model as closely as possible. These beforementioned games represent very complex game systems that are not found anymore in todays strategy game shelves - mostly for market reasons and the problem of GUI - some of these games are still played by hard core strategy enthusiasts.

I advise to search for the games mentioned above to find out whether some instances are still running.