I seem to be stuck on this quest. The first attempt I made, i was able to storm the fort and got to "5% remaining" at which point there were no stormcloak soldiers left to kill and I could not complete the quest. I started over and got the same problem. I then went back to a previous save and redid the prior mission and now I seem to have a bigger issue...there are no imperial or stormcloak soldiers present at the Fort when I arrive.