Aw, nothing for how to be a Marshal? I personally liked the gritty tactics, steel and blood, than the desk with cute little chess pieces.
Ok, ok. Anyway, y'all might be wondering: "No way, Artemesia actually has something useful to say here?" And the answer is: "Possibly enough to make the minimum to survive as a post in this rather serious thread."
So first things: I think that the General has no extra buttons to press than any region lord would. Lords can access Assign, View Armies, and Sponsor Army. I think the General has some small perk in seeing the composition of all armies though. But otherwise, the least button-intensive council position. Also one of the hardest in terms of playing BM as a strategy game because you're taking care of the strategy! (Assuming, you know...that your realm actually battles.)
So what do you do to keep up organization? Well, most realms have a Military Council or whatnot. Your Ruler should make one if there isn't one. If you never battle anything except the occasional monster or undead, then you should still get your Ruler to make that message group and include you and all marshals at the very least. If nothing else you have a place to discuss how your afternoon tea tastes.
In addition to opening the Military Council group for discussion, you should contact your marshals regularly. They're the guys who actually do the everyday maintenance of your armies. They will be responsible for getting the nobles with their units to actually move, to recruit the right numbers, get the proper paraphernalia, have the right settings, etc. So talk to them regularly so they know you're alive and not eating hot muffins while pushing around cute ivory chess pieces on a map of your continent as you ponder your role as a general.
I guess you could talk to the Vice-Marshals as well, because they're technically part of the chain-of-command as well. It's good, I guess, but not absolutely important unless they approach you or request it or something. Hey, no point in including people who aren't interested, you know.
So when giving your orders, it's good to be clear about what you want while not encroaching on the marshal's authority. Tell them what general army size you'd like to see, what the purpose of your next couple moves is going to be (As that can illuminate just why you want a certain unit composition/size as well as paraphernalia, and the route you'll take), and a general timetable. These last two are very important as a general. Capable marshals know what sort of numbers their nobles can maintain, so your job as general is more about the bigger scope of things. You need to let them know what to expect and when to expect it, so they can actually make the preparations. Don't be the general who, after finishing his muffin and checkmating an imaginary opponent, goes outside and tells the marshals "Hey march out tomorrow to lay siege to the great walled city of Illium!" It's not going to work. Achilles is going to give you the finger and walk away.
And now, we get to how modern BM diplomacy makes a huge mess of battles. For the purposes of this discussion, I will focus on the diplomatic effects, and not the individual unit settings effects (As that would be more appropriate for a marshal guide). One versus one is fairly simple to understand. Let's give A and B as two realms. A and B are at War: They fight...obviously. A and B are neutral: Consult unit behavior. A and B are at peace: They don't fight (Exception: Check marshal guide). A and B are in alliance or federation: They don't fight (Exception: Check marshal guide)
So now we get to the seemingly utterly chaotic and unpredictable 3 realms and above. They play like RTS games' multiplayer FFAs, that is, if one player consistently went AFK.
Let's bring back A and B, and add in C. Now, you should be aware that at this point, territory matters. Let's say that we are all in a region owned by C. If A and B are at war, A and C are allies, and B and C are neutral...Nothing happens. No, seriously, I kid you not. I once had this happen earlier this year, and my troops were set at murderous.
Ok, somewhat not very simple logic can be left for later. Let's go for the more obvious ones.
A and B are allies, C is mutual enemy: A and B generally deploy together to fight C if no other forces are around.
A and B are at peace, C is a mutual enemy: Generally A and B will both deploy independently to fight C. I believe that is the case, though I have seen relatively few of these.
A and B are neutral, C is a mutual enemy: It should be the same as above. Again, I have seen relatively few of these.
After those three, when you have more than a one-dimensional war status, things get complicated. Factors such as region ownership, attacker/defender, and relative diplomacy priorities get into play. I'm not going to get into it here because that would probably require about a small textbook to explore fully.
In general (Woohoo, punnerific), try to make sure those who fight with you have the same enemies as you, and the same friends.
