Next session I'm throwing my poor PC'n into a major battle, won't say details as they might be snooping around. What I was wondering is if anyone here have good ways of dealing with this? I'll most defineatly be using formations from Enemies of the Imperium as enemies, but what about allies?

And how do you "arrange" the battles? What works best for the narrative and rulewise in your experience?

I've had this come up a few times before, and part of the answer is based on scale.

Example #1, My PCs were holding a listening post against a Dark Eldar raid. In this instance, they had their squad, two PDF squads stuck in the area, and a heavy weapons squad. All in all about 35-40 troopers. At this sort of "platoon" scale I handled it by asking the players where they set up and where they ordered the PDF troopers to, if they divided troops, etc. etc. Anyway, any location where a PC was not stationed/physically present, I simply assigned a strength to. For NCOs or leader type figures I assigned three points, for heavy weapons two points, and one point for a normal trooper. I'd then adjust for any tactical considerations (Half a PDF squad was put in reserve to shore up flagging fronts). Following that, I assign scores for attacking forces in roughly the same way. Combat commences. The PCs are expected to do their thing and I just roll quickly for any NPCs who happen to be with them in their little slice of the action. If they are fighting with a large number of NPCs that they cannot take command of or are unwilling/unable to then I'll simply formation them up and fight on as usual. Again, best to use some common sense here. When my PCs didn't immediately assume command of the 4 PDF troops they had put on their part of the front, I only had one or two attack each turn and I made comment on their general ineffectiveness and excessive cowering. The squad Sarge picked up on it and quickly rallied them into a small personal formation. While the PCs are doing their thing I'll roll each round for the assorted fronts. Normally a D10 + Allied Strength versus D10 + Opposing force strength for each front. The unit that wins will chip off a point (or d5 if you feel like it is particularly suiting. IE: Massed orks charging two heavy bolter teams) Keep in mind the math starts to fall apart if you get much bigger than squad-platoon level, or if you allow a massively numerically superior foe to slam repeatedly into a lesser opponent. In such a case, you might automatically tic off points from the larger side even if they win the roll-off. It might also be effective to ignore enemy strength all together and just assign them a static value for how hard they hit your allies each turn, especially in a case where the enemy has effectively limitless resources to devote to this small scale battle. If these fronts are within visual range I allow a free awareness roll of varying difficulty (Lighting, distance, battlefield obstructions, smoke, elusiveness of enemy, etc.) to see how things are panning out. Otherwise if the group has vox or non-visual coms I replace the awareness roll with a Tactica roll. If a front is suffering too heavily I'll usually ask my players if they wants to direct troops there, call in support, personally go seize command, order a fallback, etc. Give them an opportunity to assist and flex a little tactical knowledge. While they might not have any command in a given situation, they can still lend aid or at least report a failing to superiors (Who might then order them to shore up a flagging area while still doing their own objective) or tell them to assist if able. Overall this keeps it short and easy to keep track of, but also lets the players have some sort of say-so and impact on what is going on. In addition it allows for a worsening situation. In my run the players simply couldn't afford to prop up the heavy weapons team and when they finally were cut to pieces, suddenly my PCs were dealing with Eldar slamming into their flank. It goes from "My GM is just throwing more enemies at us!" to "We lost the bolters and we're compromised, can we get everyone to a new defensive line?" You create a changing battlefield that they helped shape!

Anyway. Example #2. My PCs were told to hold the line against an oncoming 'nid assault along with several thousand guardsmen along an extensive defensive line. When you get into company or higher level engagements you get into a little more tricky territory. You could just zoom in and focus on your players little slice of the battle. This 50 meter line of trenches and flakboard and the enemies directly assaulting it. You might play up how things are going to the left and right flank so the players can prep for threats that get through there (and at this point the outcome is really more narrative) This works fine but it does run the risk of getting bogged down unless you throw in a changing battlefield. Steal a page from L5R and toss in some battle events. Maybe they start off trying to pick out high threat targets in the oncoming rush, then are ordered by an officer to charge, the charge falters and PCs are left to scramble back to the defensive line while moving wounded and holding off fierce melee attacks. The other route is taking a company or regimental level approach and wielding the PCs like a weapon. Say your squad of PCs are attached to a siege regiment and are being asked to slam through some sallying defenders and punch an opening in their fortifications, then hold it until reinforcements can move in. Always describe the action as what the whole force is doing. The Captain is pushing orders down to affix bayonets while the various heavy weapon squads are loading up fresh belts. Your Lt orders the charge. You don't worry about exact numbers, you just throw enemies headlong at your players and if they ask for numbers don't offer a solid figure unless they want to burn a turn just surveying the field. Give them a sense of being part of a larger conflict, give them rolls to break off an attack and lead a whole enemy platoon into a killing field for the massed support weapons backing them up. Let quick allied formations fight and die while the squad throws flares to mark artillery, let the PCs suppress an enemy marksman dropping friendly NCOs or officers. All the while you are taking notes and assigning numbers. Your PCs were slow here, it cost lives. and you deny them a formation here or you hold back some support here. Basically you use the same tactics are the first option, but you grant the players a constant (if dwindling) stream of support so long as they keep getting positive results. One of the great advantages here is they can lose an objective without losing face or their lives. They are ordered to fall back after the defenders shred the demolitions team. Tough, your PCs did their best but luck wasn't on their side. Now they are forced to scale walls the old fashioned way after regrouping.

Hope that rambling post helps! I'm also curious to see how everyone else does their large battles.

Nobody?

I prefer squad versus squad but for larger battles I use slightly modified hordes from BC against the players.

For truly mass combat, I use the mass combat rules in BC tome of blood, switching repeatedly to the players in a smaller focus. In those rules, both sides have a combat strength which equals WS/BS and the first side to score a MoS of 6 or more wins. I describe each round as a part of a major battle and the actions of the players provide a modifier for the subsequent round.

I do try to provide narrative to give the impression of a major engagement. Artillery duels in the distance, troops on either flanks fighting as well so while the players focus on their small part of the battle, they still feel they are part of a large force engaged with the enemy.