Well, one can assign Generals to various "battleplans:" frontline, offensive, spearhead, fall back line. All of these have "planning time" (time to complete the plan), and there is a tool tip on one of the general portraits that shows the level of "preparation." It often has a max value in the 40% ballpark and may gain 4% per day, etc.
Even without consulting the non-existent manual, the game makes it pretty clear that using these "battleplan" features, instead of just manually moving divisions and armies around is a beneficial exercise for the player, i.e., not just an interesting interface that allows the player to arrange and deploy his forces using the same algorithms the computer opponent does. But the specifics of HOW the use of these battle plans are beneficial remain unclear, and many other questions too. For example,
1. What does the "40% planning bonus" I referred to above (a value I noted while Guderian was planning during Spanish CW expedtionary ops) actually DO?
2. I see someone refer to "expired planning bonus" but so far I have not encountered any description of that.
3. I noticed that the way the battle planning UI functions is slightly different if I use the Field Marshall to activate it. Often areas I "paint" with the cursor after selection front or offensive or spearhead from the FM tab are red, whereas they are green when selected for one of the subordinate generals.
Should battle plans be done at the Div level or the Army Group level? Is there any difference? Subtle differences in the UI and feedback from the UI on how things have changed after planning, etc. suggest that the battle planning DOES function differnetly when plans are set at the FM level than at the Div level.
4. Taking it down a level, what about individual Divs? I've tinkered a bit with using the "Div Assignment" and "Edit" functions and while I've managed to achieve a "multi-level" battle-plan assignment, I'm not entirely clear why I would want or need to, nor how a "manually" adjusted one would differ from the top-down plan.
Lets us say for example I have Moltke as an FM (too old for this game but I remember the name) and Guderian is an army general. I set up a front with Molke and he distributes Guderian and any other armies. If I want to launch an offensive at one spot, I could either use the "offensive line" tab in the Field Marshal or General OR I could just select some units and then use either the hotkey or the button on any of the tabs and then assign specific divisions to engage in the offensive.
While all that stuff wasn't too hard to figure out by tinkering with the UI in game, the relative pros- and cons or any mathematicaly adjustments that are made are unclear.