@Imperious:
The only way to make a balanced game is to allow Historical developments at specific times, not variable. American entry was assured after the Zimmerman note no need to figit with what happened. If it does not add to the game it does not need a place in the game. Axis and Allies is a broadstroke of History put in a game. It’s not supposed to account for every single incidental because these types of rules bog down an otherwise good game.
So Global is not balanced and has no chance of being so? That game has plenty of variable entries, left up to factors determined by player choice.
If Russia is trouncing Germany and is twice as rich as when it started, would it make sense that it’s people be disillusioned with the war and that they revolt?
By the logic quoted above, who cares? Revolution turn X, even though Russian morale is at its highest in decades! Huzzah!
If Germany has pulled back all of its subs and surface fleet to defend its home waters and elects not to violate belgian neutrality, would the UK (not to mention the USA) have been as gung-ho about entering, or even entered?
By the logic quoted above, who cares? USA hasn’t been provoked at all, but, TO WAR!
Scripting the events of the game while completely ignoring the developments in the game is what is truly ahistorical.
Thinking of history as a set sequence of events that couldn’t have happened any other way is dangerous when it comes to analyzing how and why events occurred. A historical game would be one that takes the miliary success into account when determining if a nation will have a revolution, not ignoring all of that to keep a schedule that is based on a succession of events that could very well look nothing like what is happening in the game.
A historical game takes the causes and effects in historical patterns into account, not insisting that events be maintained on a schedule no matter what, no matter how much the previous events deviate from the real-world script.
The central powers being caught between destroying the enemy and avoiding angering the US only adds to the potential for the game to avoid being played the same way over and over again, getting boring in a couple months.
Unless you believe that because of the variable entries in global (not the sheer size of the game), it is impossible to balance, there is no reason to believe that  in WWI variable entry/revolution is an automatic balance killer.
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Imagine this scenario:
The CP are focusing all of their effort on knocking out France, keeping only enough in the East to ensure the safety of their most important territories.
Russia is booming, entirely safe for as long as France can hold out, and Russia is in fact doing well enough that the Central powers may have to divert attention from France to ensure their defenses hold. Conceptually, we would imagine that morale in this scenario would be higher in Russia than it was in the war, as the CP made huge advances into Russia and the situation was looking grim.
But whoops! Turn X came along! Russian Revolution, against all odds! Russia is out of the war or whatever. France stands alone. CP wins.
It’s quite plausible that if Germany knows that the revolution will happen according to a timed script, rather than factors that would logically lead to the revolution, they can ignore russia only enough to keep from taking Vienna or Berlin or whatever, and then once the revolution happens, they are home free.
Is it possible to balance the game with this possibility? Probably. But how bizzare would the game be? France has to be strong enough if Germany decides to ignore russia. But if France is that strong, will Germany have any real coice or motivation to go after Russia?
Similarly, UK and France KNOWING when USA would enter would allow them to do some historically (from a pattern/plausibility point of view) asinine things.
How can the game be historical when both sides know when these huge events will happen when in reality they were much muddier?
Obviously we don’t know all the details of the game, but scripting the game has a very good chance of making balance MORE difficult, especially with the case of Russia. Unless you want to throw out the revolution altogether.
Having a simple system that tracks the US involvement and Russian Revolution presents its own challenges, but if far from impossible to balance, and may be easier to balance than a game where those two are scripted.