If you have aligned yourself with the Stormcloaks and not the Imperial Army, Battle For Whiterun is a quest in which war is declared on the city of Whiterun. Ulfric Stormcloak wishes to take over the town, as it is in the middle of Skyrim and serves as a major strategic city.
The player heads of the front line to find Galmar Stone-Fist rallying the troops, they are also being supported by three catapults, firing missiles that are on fire. (The player can fire these, but it doesn’t benefit you in any way)
You charge across a battlefield to the gate of Whiterun, where there are many Imperial Legionnaires supporting the Whiterun Guard.
At the first hurdle, there is a barricade, it is split in half so the player only has to knock one down. You then have to climb up onto the wall and lower a drawbridge to the main gate.
When you enter the city, there are many barricades and Guards trying to keep you away from getting to Dragonsreach, but you can overthrow these barricades pretty easy, as you have a lot of support.
When you get to Dragonsreach, Jarl Balgruuf the Greater sends three guards down to the player, these men should be one hit kills. As you head up the stairs, the Jarl and his assistant, plus two guards, will be waiting.
After a fight, the Jarl surrenders, and Whiterun has officially been conquered by the Stormcloaks.