So we had this siege.
The strategy played out thiswise:
Before the party even showed up at the fortress, the undead army (mostly outside the fortress) had managed to take the northernmost tower.
As you can see, the party took 300 of their 500 troops and placed them at the other end of the bridge connecting the rest of the fortress to the tower, joined those troops and began their attack there.
The girls had the remaining defenders (200) spread evenly out across the whole fortress. (Entrances to the fortress are picked out in pink. Those little mousetrappy things are catapults.)
So then the party started charging across the bridge, with their troops in tow.
DMwise, the thing then is to figure: ok, assuming the party's doing this then what does the Death Knight or necromancer in charge on the other side do?
Obviously, the guys on the north tower defend themselves, and that's where most of the action the PCs could actually see takes place--the Battle of Styrofoam Cup Bridge.
Meanwhile however, we got the other 900 undead outside the fortress. What'll they do?
They could just let the tower guys try to hold the tower, if they do, great, if they don't, they can just stay on the ground and keep starving the inhabitants, but if the PCs realize the undead army's not moving then they can bring all their troops to bear on the north tower and the skeletons will probably lose that position pretty fast and all for nothing.
So the skeletons attack some of the castle entrances in order to draw off some of the defenders.
They go for the west gate because if they break through, then they pincer the party and the rest of the bridge attackers, and for the east gate because it's waaaay on the other end of the city/fortress, so it's hard to transfer troops over there.
Now attacking a castle isn't easy, as everybody knows, but the skeletons do have overwhelming odds--at least in the beginning. So while the PCs and their troop square off 300 to 100 up north, there's 450 skeletons on the east gate and 450 on the west gate--each facing less than 100 defenders (it took a while for the party to decide to hustle everybody over to the gates).
The odds are still pretty decent for the defenders, but you have to take into account the fact that arrowfire isn't especially effective against skeletons and other bony undead.
So anyway, up on the north bridge, the party is more-or-less kicking asses and taking names. Mandy and a helpful carrion crawler (long story) blocked up the middle of the bridge, Kimberly ordered the archers up onto the styrofoam cups so the skeletons couldn't sneak around and leap cup to cup, and Connie figured out that the floating tattery guy can only be hit by magic weapons.
On the other fronts, though, I'm rolling dice and the skeletons are making steady progress at the gates. They rolled surprisingly well.
After a few rounds, the invaders were charging into the east tower, (there was fighting in the stairwells) so the girls decided to pull all their east side forces back to the base of the bridge (there's a blue circle there) so the skeletons would be out in the open and they could shoot at them with the catapult. (Not sure how the people who live in the city felt about that move, but oh well, that's what happens when you put PCs in charge. Goddamn drifters, no respect for property rights.)
Here are some casualty markers Reaper sent us:
So the thing is--all goes well for our heroes as far as what's in front of them--but things are looking distinctly gruesome everywhere else.
Time is a big issue in this kind of fight--a combat round is 6 seconds in-game. But the idea of the PCs getting updates from the other fronts every 6 seconds is preposterous. (And they can't see the others very well.) On the other hand, a combat round is about a half-hour real-time of moving and deciding and rolling (twice that when Frankie is playing) so if you limit the arriving update couriers to, say, one a game-minute, that's still basically one update per session (I limit full-on rolling on the battle of styrofoam cup bridge to the party and anyone immediately ordered by them--mostly only folks who can fit on the bridge, so it's only about 10-12 pairs of enemies per round.)
At that rate the strategy element in the rest of the fortress is so slow that it's invisible to the PCs., which means it's barely part of the game. I split the difference on the side of "easy" vs. realism at one update every 4 rounds.
Everybody's been pretty busy the last 3 weeks (every porn parody on earth--including Batman xxx--has decided they need to hire KK since she won Best Actress) so we haven't played in a couple weeks.
Nobody knows exactly what that boss skeleton in the armor on the horse is up to. He's been hanging back. Find out soon though, I figure.