Skyrim:Rescue from Fort Neugrad

Quick Walkthrough
# Speak to Galmar Stone-Fist.
# Meet the Stormcloak rescue party.
# Sneak in the cave or fight your way in through the front gate.
# Free the prisoners.
# Eliminate the rest of the Imperials.
# Return to Ulfric.

Detailed Walkthrough
thumb|right|The secret entrance under the lake
Meet the Stormcloak Rescue Band
After reporting to Galmar Stone-Fist in the Falkreath Stormcloak Camp, he tells you that your current objective is the Imperial-controlled Fort Neugrad where some of your brother Stormcloaks are being held captive. He has sent scouts ahead to the fort, so meet up with them for further instructions. When you meet up with the scouts speak with Ralof, who will be quite happy to see you. He will tell you that they have located a cave under the lake that should lead into the fort's prison. He will ask you to sneak in, kill any Imperials you find, and then release the Stormcloak prisoners.  After you have released the prisoners, head to the courtyard where he and his men will join you in fighting the Imperials.

Follow the quest marker around the fort to the lake. Be careful not to get spotted by any Imperials or you will fail that objective and have to storm the fort. Once in the lake, swim down and you will see a small wrecked boat with a locked chest slightly hidden under it. Directly behind you is the entrance to the cave.

Rescue the Prisoners
The passage at the bottom of the lake will lead into the prison level of the fort, through the natural cave at the southeastern corner. Eliminate the Imperial soldiers in the prison room and get a Fort Neugrad prison key from them (there should also be one lying on top of a chest in the same room).

Open the cells and the Stormcloak soldiers will run to a chest to acquire weapons and armor. Talk to one of them and he will ask you what to do: you can tell them to wait where they are, or follow you.
To guarantee they all survive, you may instruct them to stay behind, and return to them after the fort has been taken over. If you tell them to follow you, they will participate in the upcoming battle and may die, although this doesn't seem to have an impact on the quest.

Take Over the Fort
As you leave the Fort Prison level and reach the courtyard, you will engage more Imperial Soldiers. Ralof's band will join the fray once you start the fight. After the fight, you will have to go inside the fort to eliminate the rest of the garrison. You can have Ralof follow you, or tell him to wait out in the yard.

Once the Imperials and the fort commander are dead, talk to Ralof and he says that he will stay and clean up the mess. That ends the quest and starts the next stage in Liberation of Skyrim.

Notes
If you kill the prisoners, that part of the quest will fail, but Ralof and his men will still join you for the battle in the courtyard.
Openly entering the fort with a follower or two and letting them defeat all of the Imperial soldiers may be a useful way to avoid many, if not all, of the myriad bugs that can occur with this quest.
Completing this quest deposes Siddgeir as Jarl of Falkreath, and installs Dengeir of Stuhn in that position. Siddgeir will move to the Blue Palace. Dengeir has two personal favor quests which cannot be started if he is Jarl.
If you have Serana as a follower during the assault, she will often reanimate Imperial soldiers that have already been killed, who must then be killed again to complete the quest.
If you kill all the soldiers before you interact with Ralof, he will not be at his post and you will have to restart the mission

Bugs
 
Reload a save from before the quest was received, completely clear out the fort of all bandits, and then receive the quest from Galmar Stone-Fist. Reloading a save from after the quest is received will not fix this bug.
 
 Using the console command   will teleport you into the cell of a prisoner you are supposed to rescue. Getting out of the cell will require picking the lock.
 
To solve this, use the console command   and   to turn off the combat AI and the AI globally, sneak past the fort and enter the cave. Then when loaded inside, turn both back on again.
 
One possible solution is to transform into a werewolf away from the soldiers surrounding Ralof, and then kill all of the soldiers. Once that is done, Ralof himself will ask you to get him another garrison of troops. After you retrieve his soldiers, you should be able to continue the dialogue. Alternatively, kill all the troops and then use Voice of the Emperor (if your race is Imperial).
Another possibility is to fast travel somewhere if Ralof is not at Fort Neugrad, then fast travel to Fort Neugrad. Ralof will be approaching the entrance to the fort and can then be engaged in dialogue. 
 Another possible solution is opening the console and entering  setstage CWMission04 20  if the prisoners lived or  setstage CWMission04 21  if the prisoners died.
 
 
To complete the objective, order the freed Stormcloak prisoners to wait in the prison, then climb up the ladder exit to Skyrim and reenter the prison from the same exit.
 
 
 To fix this, move away from the fort and use the console comands  prid 0001B133  and  moveto player  to move Galmar close to you and away from the fort. Talk to him and initiate the quest. If you plan to sneak into the fort, use the command  setobjectivecompleted cwmission04 12 1  to complete this objective and proceed with the quest.
 
 If he does not advance the quest when talking to him then open the console and enter  setobjectivecompleted CWMission04 50 1  followed by  setstage CWMission04 100 .
 

Quest Stages