The walls of Whiterun are defended by the Whiterun Guard as well as heavy support from Imperial Legionnaires sent by General Tullius. The first archway is blocked by a simple wood barricade that is easily undone by any offensive attack upon it.
Arrows and death will rain down from all directions upon entering the lower courtyard. Battle through the opposition and head up the battlements around the left side of the drawbridge. Directly above the bridge is the windlass used to lower it. Once the gate is lowered the defending troops pull back into Whiterun proper, allowing for the Stormcloaks to follow and continue the onslaught.
The battle rages on on the streets of Whiterun. Several of Whiterun's populace can be encountered on the streets but are non combatants and it is still considered a crime to attack them openly. Battle through the districts and barricades towards Dragonsreach where Jarl Balgruuf awaits. The Jarl is guarded by two waves of three guards and is flanked by his trusted Captain Irileth. Kill the opposition and beat the Jarl into submission to secure his surrender. This is a great opportunity to stock up on steel arrows if you´re low since all of the guards of Whiterun and the Stormcloaks have at least ten of them in their inventory and a lot of them die.
With the Jarl on his knees, he will agree to surrender and promises to gather his belongings and depart. Vignar Gray-Mane enters the hall bellowing "Balgruuf!", where-after Balgruuf and Vignar exchange words supporting each of their camps. Balgruuf cites that the Empire needs Skyrim as much as it needs the Empire and that the Nords are the backbone of the Empire. Vignar argues that the Empire is nothing but a puppet of the Thalmor and that Skyrim should be free of the Empire, eject the wicked "Witch-Elves" and be free to rule themselves under the mighty Talos. With Vignar on the throne, return to Ulfric for further orders and a reward.
The Battle-Borns get bullied and they are robbed twice. They blame this on the new Grey-Mane run government of Whiterun.
Adriane Avenicci's dialogue will change.
The preacher of Talos, Heimskr, becomes a very happy man, even though he cannot enter his house, for it is sealed with debris and is missing most of the roof. Instead, he has a small tent next to the wall surrounding Jorrvaskr. This means a quest from the Thieves Guild from Vex cannot be completed.
The town has a few scars from the battle. The area around the Gildergreen tree is badly damaged.
Jarl Balgruuf, Commander Caius, Hrongar, Proventus Avenicci and Irileth take up residence in The Blue Palace in Solitude. Note that traveling there and speaking with them means that they regard you with hatred and speak of "when we retake Whiterun". Irileth is known to speak of the many dark ways she has dreamed of killing you since your last encounter.
NOTE: If you follow the Jarl to his quarters after the fight, Galmar will become hostile when you kill the whiterun guards before they become hostile. It is unknown if this is a bug. So after you go in to Dragonsreach, wait for the Whiterun guards to become hostile before you kill them
Severio Pelagia's house is no longer accessible, due to debris blocking the door and damage to the roof. Heimskr's house is also inaccessible, for the same reason.
It is sometimes possible for the fireballs launched from the city onto the plains to become stuck there. Waiting and fast traveling do not fix this. Another possible bug; if you quickly talk to the Jarl of Whiterun after defeating him then he will constantly say "Give me a few hours to gather my stuff, and I will depart. You have my word." Therefore you are unable to complete the quest. To complete the quest you have to wait for about one minute and the quest will complete automatically, if nothing happens try attacking the jarl again when a new guard walks in. If he sees you attacking the jarl you get a bounty (40 gold) but the mission will continue.
When traveling to the Stormcloak camp in Whiterun, and leaving the camp by fast-traveling to for instance Riften, occasionally completes the quest instantly. When reporting back to Ulfric, he will call you a coward, but it does start the next quest (the Liberation of Skyrim). Also if you fast travel to Windhelm AFTER you enter Whiterun, the same thing happens except Ulfric doesn't call you a coward.
If the above happens, Whiterun wont have any changes, except that Whiterun will now be counted as a Stormcloak city.
When reporting to Ulfric after the Battle of Whiterun he may not give dialogue to continue the mission. Whiterun will remain destroyed and the Civil War storyline cannot complete also. Possible fix: type the following console commands : stopquest cwobj; startquest cwobj; getqr cwobj; Ulfric then spoke the dialogue. Please confirm.
On rare occasion, after you have killed a guard in Dragonsreach, Galmar will start to attack you. To correct this, reload the autosave and don't kill anyone. The game will continue. It is possible that this is due to the game sometimes applying a bounty to you for your action and Galmar is very intolerant of criminals.
If the Thieve's Guild quest, the shill job for Heimskr's house is triggered after the battle for whiterun, then you cannot complete it, due to roof damage and entry points blocked by debris.
Sometimes the Stormcloak Soldiers present during the quest do not clean up properly after taking the city. If you return a few days later you can see 3 or 4 soldiers standing around doing nothing. (Most commonly found outside Dragonsreach and the main gates).
The Battle for Whiterun scripting may not initially take affect on the city meaning that when you enter Whiterun to force the Jarl to surrender the guards will be standing by the gate as they do usually, the prophet will be preaching by the Shrine to Talos and the cows and other people will be running around as the fighting suddenly starts all around them. (Note that attacking any guards or anyone else when this happens will count as an assault and give you a bounty). Reloading from an earlier save should fix the problem.
Critical bug appears when you have to accept Jarl surrender. Sometimes, spite the surrender, Jarl says the words, the mission does not continue. This happen when you win the Dragonsearch battle without fight (hit) with Jarl the greater. When you leave Dragonsearch without that part of the mission (Accept the Jarl surrender) it fails. And if you starts to fight him again, Stormcloack soldiers will attack you.
Sometimes when inside Dragons Reach none of the NPC's are hostile towards each other and the player and even after forcing Balgruuf to surrender he will be classed as "busy" and the quest will stay stuck on accepting his surrender. In that case using console command setstage cwsiegeobj 9000 may be used to finish quest and start Liberation of Skyrim.
In Whiterun city during the quest, it is possible that some of the children are still outside, if you accidentally hit them, you will get a bounty (40 gold). If you complete the quest after getting a bounty, you will be unable to remove it; You cannot talk to any guard in Whiterun hold to pay your bounty as the Stormcloak soldiers in Whiterun (city) will be unaware you have a bounty and even though your bounty is only 40 gold, you will be attacked on sight by the rest of the soldiers in the hold, nor will they accept your yield. Currently, there is no known way to remove the bounty other than loading an older save.
If the Alik'r warriors from the quest In my Time of Need are still present in Whiterun (due to a glitch or otherwise), attacking them will accrue a bounty. However, the bounty will be in Eastmarch, not Whiterun.
After you leave Whiterun after you force Balgruuf to surrender, there will still be Whiterun guards in Riverwood.
If the quest is active, but the player has not started the battle yet, being teleported into the city via either completing the quest A Night to Remember (If the quest was started at the Bannered Mare) or by getting arrested and being sent to jail (Unconfirmed) will cause the quest to become automatically completed upon leaving the city with no battle taking place. Balgruuf the Greater will remain Jarl and the Whiterun Guard will remain as the city's guards, but all other NPCs will act as if the city had been taken by the Stormcloaks.
If you own Breezehome before the siege, you may lose Breezehome as your home afterwards. If you do not have your key you won't be able to get in. You may buy it again from Brill (the new steward) but chances are he may be lying in the streets dead, naked. If this is the case you cannot get Breezehome or your items back.
Edit
Added by Bödvar
