Where did I mention 'undoing' the events of a game session?
You said:
the rationale behind them, to back up your claim (if your players request it; probably after the session so as not to unduly reveal important details as well as bog down the game session itself)
So they only know why it was no-win after the fact - and if they point out a "but we could have..." then you "give credit wherever its due for having managed to find a creative and involved group of players.".
I've yet to see anything from you, rule or otherwise, that would lead me to the conclusion that a claim of 'a mob of mortal mooks, even a large mob armed with assault weapons, is NOT an undefeatable plot device' is incorrect. If you'd like to start stepping up to that plate, please, feel free.
I referred to hundreds of cops - FBI, SWAT, etc. If you want to view such as complete mooks, then that's fine with me.
But maybe I assumed that others would know how the police operate in situations like these. Note: basing this off of numerous reports, like
http://militaryvideos.tv/news/continuing-swat-raid-errors-and-pranks (where 50 - 60 officers were dispatched to deal with a report of a hostage crisis) and of countless online reports of how search warrants are serviced on suspected drug dealers.
So here's an expanded version of: "They're pinning this whole mess on you. You can expect the tactical unit, SWAT, the FBI, Homeland Security, and maybe a hundred local cops to come to your door as soon as they get their warrants. You've got maybe an hour."
First - the standard "high risk search warrant" activity.
Units arrive at intersections surrounding house, cordoning them off to civilian traffic (reducing the number of people in the area) as the rest of the task force goes in. Units arrive in the front, back, and sides of the building with military precision. If they follow their SOP then:
"Police generally break open doors with a battering ram, or blow them off their hingeswith explosives. After an entryway is cleared, police sometimes detonate a flashbang grenade or a similar device designed to disorient the occupants in the targeted house. They then enter the home under its cover. SWAT teams have entered homes through fire escapes, by rappelling down from police helicopters, and by crashing through second-story windows. "
But that's drug raid procedure, not homeland security. Add a small fleet of police helicopters, probably surveillance drones, a mobile command centre, FBI sharpshooters stationed on any nearby building (or anywhere they can get a good line of sight), the bomb squad (possibility a military one to deal with the terrorist who blew up that building), and every department that wants to be in on the arrest. Since we are dealing with Chicago the Special Functions Group, the Targeted Response Unit, the Mobile Strike Force, and SWAT would be there. Call it 30 men from each of those units, plus roughly an extra hundred regular officers to provide backup and support services (directing traffic, keeping bystanders out of the way, etc), plus a squad from the FBI, a squad from homeland security, someone from ATF, and so on.
The TRU would move in first, surrounding the building, with the others in reserve. They'd treat it the way they would treat any high risk search warrant - with the exception of there being an FBI agent to "officially" knock. I.E. a member of the TRU (in body armour) would pound on the door while the agent called out "This is Special Agent Tilly of the Federal Bureau of Investigation. I have a warrant to search this property and detain its occupants for questioning regarding last night’s explosion. If you do not open this door, we will be forced to break it down."
Since the federal agents are in charge, they would probably wait 15 seconds before trying to break down the door - using the "15 seconds to open the door" rule as opposed to the "5 second to keep him from disposing of evidence" rule that is used in many drug searches.
Should a ward be in place, the first blast would take out the ones with the battering ram. Hearing that, the men at the windows would try to bash them in (to toss in flash bangs) and go down themselves (assuming that the windows are warded, because anyone who doesn't could have a pipe bomb tossed through the window on his day off and learn from that...).
With officers down, the other officers would begin opening fire on the house in an effort to provide covering fire. Regualarly armed officers would be using handguns, Remington 870s, Mossberg 500s, and semi-automatic AR-15s. SWAT would be using submachine guns (probably one of the following list: 9 mm and 10 mm Heckler & Koch MP5,Heckler & Koch UMP,[11] and 5.7x28mm FN P90), combat shotguns (Benelli M1, Benelli M4, Benelli M1014, Remington 870, and 1100, Mossberg 500 and 590), carbines (Colt CAR-15 and M4 and Heckler & Koch G36 and HK416), sniper rifles, and lobbing tear gas at the building. There would be ARVs (Armored Rescue Vehicles) on standby - and some police departments mount rams on these armoured vehicles, so seeing an Alvis Saracen modified with a ram wouldn't be out of the question.
That amount of gunfire has a tendency to put a lot of holes in walls. If the ward keeps the bullets from doing that then that would use up some of its power. Otherwise hiding in the bathtub is your best chance to stay alive as the bullets perforate the walls.
Three to five seconds later someone would call "cease fire" and maybe 3 - 5 seconds (or more) later everyone would finally stop firing - but would be ready to start again if spooked. The bodies of those hit by the wards would be retrieved, someone would get on a loud speaker calling for a surrender while the bomb's squad remote unit would try to clear to the door. Once pronounced "clean" (that is, no signs of bombs were found) the next wave would move in to plant explosives on the doors and window. If the wards trigger when they do that, they go down and there would be another mad minute of gunfire (wearing away the ward or putting bigger holes in the building). If not, the ward would have to handle shaped charges trying to blow holes in the building.
After than the building might be rammed by one of the ARVs (I see that as a real challenge to any ward) , a seize might happen, or extra forces from Homeland security might be called in to help level the building. Note that all the assets mentioned so far can be found in the hands of Chicago PD and as officers go down additional one will rush to the scene. I'm not saying that all 12,244 members of the Chicago PD will rush there, but a thousand or two? That could happen.
The average cop would use the cop template. For the police officers in special units I'd model them off of the SI template - giving them an aspect to tap and maybe one stunt with at least a Good weapon skill. Trained marksmen would be better than that, call it Great weapon skills to go with their weapon 3 - 4 guns.
With officers down, there's a very good chance that anyone who shows himself will die "resisting arrest" and it will be a "good shoot". Say that if the door opens without warning a couple of dozen officers will shoot the attacker coming at them - emptying their guns and maybe pausing to reload.
Now how does a PC easily beat that in combat? Or do they avoid combat (as suggested in the original post).
With that many people involved, any PC who's there when the raid happens is going to go quietly or in a blaze of glory.
Do they run, go underground, hide out, veil and watch the operation, use this as a distraction to hit another target, have sniper positioned to take out officer Rat Face (long standing NPC who's behind the raid), or do they do something else?
Personally I still think that we are talking plot device here. The raid is happening and if resisted it will be met with lethal force.
Richard