[1] http://www.amazon.com/How-Make-Fourth-Edition-Comprehensive/...
[1] http://www.amazon.com/How-Make-Fourth-Edition-Comprehensive/...
It seems that from that it really wasn't the American's accuracy that enabled their simultaneous fire, but rather the American's understanding how important coordination was with artillery and starting from just after WWI working on making that a reality.
Reading this article makes me want to play one.
You can find the free version of SPWAW at the SPWAW Depot: http://www.spwaw.com/
Players tend to be around in the evening GMT. Contributions weclome, either in player-hours or pull requests -- hacking in Lua, primarily, with some supporting tools/infra in perl and python.
The AI is excellent especially when playing the defense (which is nice, since for the human playing the attacker is the more interesting role). It's great at noticing when the player has overreached and mercilessly punishing those mistakes.
I can't recommend it highly enough if you have any interest at all in wargames. It works as an entry level game, but is also deeply satisfying for the grognards.