I believe we talked about this a million times (although we never delivered a straight answer) - we are trying to make the game less restrained by creating mechanics that globally favours strategies that are historical, instead of forcing the player into doing this at that time just because it's the way it happened.
An example of this is how we're balancing the game to make theese kind of historic campaigns self rewarding; capturing stalingrad will give you acsess to large production areas, and will secure your passage to the oil-rich caucassus, while striking pearl harbour will rob the americans of their closest naval outpost and also provide you with an air base perfect for raiding the american mainland.
Another example of this is how we're getting rid of the country border system in favour for a more generic mechanic - you can now ally and unally everyone else as you favour, but your population may disagree depending on your previous relations to this country.
In detail, it works like this:
Each country have a variable for every other country representing their relations to theese. If you are at war with a country, this value will drop some every month - while if you're allied, the values will rise. If, however, you should ally with a country that you have previously fought for a long time, there will be public unrest, and you will get a cut in your tax income depending on how badly the public dislikes your new ally.
Over time, the relations between you will raise and the debuff dissapear, but it can be impractical for a country to ally it's greatest enemies, simply due to how much income they will loose to public unrest. You also have to be wary of how you plan your wars, since declaring war on a country will give an instant drop to both your relations.
Some countries will start off with increased or reduced relation standing to eachother to discourage theese from allying eachother - Germany and the USSR have naturally bad standings towards eachother, and so does Japan and the US. Britain and the US will however have naturally good relations.
The value can vary between 50 and -50, where negative numbers will give you the debuff. Declaring war will substract the number by 10 instantly, while peace gives you nothing (only over time).
