So I am working on a battle arc for a fantasy novel which is basically a medieval/magic combo with other races thrown in. I completely scrapped a battle due to it being a discombobulated mess- very frustrating grrrrrr so now I am working from the ground up on a 'Battle Model'! References for research would be fantastic, but if that's not your style then tips and suggestions are welcome. I am thinking I may have to start with 3 markers (1 for the antagonist army, 1 for the protagonist army, and 1 for movement) and a series of numbered pages to start with before going into to more detail.
One of the top books on battle strategy is Erwin Rommel's Infantry Attacks (1935). Even Patton read it.
I take it you are not considering civil war - because for that I have a host of reference works Referring to your poll, that depends entirely on how many MC's you have. And on how complicated your plot is. In my civil war I have four MC's, wayhay! And the reader just has to cope but then a civil war is a really complex issue
Speaking from my own opinions and small amount of experience, most real battles quickly devolve into a discombobulated mess. Alexander's army once stalled in their attack because a river broke up their infantry formations, but they refused to withdraw before their enemy so it turned into a sort of brawl on a muddy embankment. I personally once sat in a vehicle turret for six hours marking empty mud huts with a GPS because a mine-roller wheel flew off. Unless you're writing a duel or a post battle transcription, don't be afraid of chaotic battle scenes and a little confusion. Sure, I need to know what's happening, but I'm not reading a football replay, with every calf twitch and finger extension deconstructed and analyzed. I'm reading about two or more large groups of people trying to kill each other, possibly with completely different tactics, strategies, and weapons. Chaos is a given. Otherwise, its going to feel hollow and boring. It'll be too clean. Definitely read Rommel's Attacks, its a phenomenal read. Feeding Mars is another good one, albeit a little dry.
I need a general strategy and a series of custom strategy for my main 5 as a guideline for how the characters will act/react to some extent, and their purpose in this battle/what role they play etc. I ended up scrapping my battle arc because it made no sense whatsoever. The battle itself, and that characters parts. There's messy then there's, "Wait, what happened?" So this is just to help me clarify the characters and armies in this arc. Thank you for the info!
Write no joke operations orders for your armies. This will help clarify force goals and frame character intentions. https://en.m.wikipedia.org/wiki/Operations_order
Well are you doing both open and guerilla warfare? Open warfare the armies will clash steel directly in mass numbers. In guerilla tactics you might want to go for a more stealthy approach, or hard hitting and brutal strikes quickly. Work on out flanking and overtaking the side you intend to lose in a given battle. Try demoralizing tactics against the intended loser, to make a victory due to the losing side having a mass retreat or give up. I have been working on multi viewpoints in my own work. Gives the reader different vantage points while on the field. Even though it is a Sci-fi, I have characters that use swords in combat, and utilize stealth and other elements to their advantage. Seems at the end of the day you can't help but utilize a versatile tool, even in a world with guns and other weaponry.
Start with the basics. Troop types for one. Cavalry, infantry, missile (archers, crossbowmen). Study the armor and the weapons. Swords, polearms, spears, English longbows, and crossbows. Now study the battles. Pydna, Carrhae, Agincourt, Hastings. Notice the quirks of each battle. Warfare depends on luck and wit. Just as many battles have been won by odd chance (like commanders being slain) as by strategy. Read up on the many examples and you'll be fine. As for POV, I'd suggest either giving to a character who can see the battle unfolding, or a character that is in the thick of it. You either want (in my opinion) the feel of the fight's brutality, or the overmatching eye of someone watching the whole thing unfold. Also, I would suggest Sun Tzu's Art of War. Hope all of this helps.