Sorry this took forever
Outcomes:
-Dragonborn and his forces skirt around the Stormcloaks and manage to harass the rear of the Stormcloak advance. The Windhelm supply caravan is injured early in the fight, and half of the trebuchets are destroyed. Dragonborn and his men retreat into the forests before the Stormcloaks can regroup and retaliate in earnest. Whiterun forces receive minimal casualties.
-Dragonborn's forces attempt to bait the Stormcloaks toward Fellglow Keep, hoping to engage them in a protracted siege. The Stormcloaks divert 4,000 of the main column into pursuing the Dragonborn. These forces encounter stiff resistance when they arrive at Fellglow Keep. Irileth's forces sally out to engage the Stormcloak contingent, and drive them back with success due to favorable terrain. It is apparent that it will be a siege unto itself to remove the Whiterun forces at the keep.
-When presented with the news of the force at Fellglow Keep, the Stormcloaks reason that a fighting force harassing their siege line cannot be tolerated if they are to lay siege to Whiterun. The Stormcloaks elect to destroy the guerrilla forces as quickly and efficiently as possible before laying siege to Whiterun. 10,000 Stormcloaks march up to Fellglow Keep and assemble trebuchets. The forward force initially sent against against Fellglow keep divides into four battalions devoted to feretting out the Dragonborn and his men to prevent another surprise attack.
-The aged, unimproved walls of Fellglow Keep along with the hastily-built defenses placed by Irileth's forces are badly damaged by the trebuchet volley. The walls are breached relatively quickly. Heavy infantry rushes into the numerous breaches to destroy the Whiterun forces within.
-Irileth's forces take substantial casualties, but also inflict their share of kills upon the Stormcloaks. Irileth is surrounded by forces too numerous and strong to fight through on their own. Disaster appears imminent, but the Dragonborn and his forces distract the Stormcloak scouts by sending harassing parties against the remaining siege engines - using the diversion to sally out of the forest against the attackers. The Dragonborn gives Irileth an outlet out of the doomed fortress and the Whiterun forces retreat with heavy losses.
-The siege of Fellglow keep lasts a day and a half, far less time than anticipated. Ulfric Stormcloak issues a forced march immediately after the engagement at Fellglow to lay siege to Whiterun before Solitude's reinforcements can arrive.
-Irileth and the Dragonborn split up; the Dragonborn attempts to head off the Stormcloak army and lay traps, Irileth uses her remaining forces to assault the remaining siege engines.
-The Stormcloak rear guard surprises Irileth's forces and enter into a pitched skirmish. Heavy casualties are incurred, and Irileth is injured but manages to retreat. Most engines are destroyed.
-The two forces return to Whiterun, only beating the Stormcloaks to the gates by a few hours. The Stormcloaks begin to lay siege, and there is no word as to when Solitude's forces will arrive.
Whiterun:
- Heavy losses incurred. 2,200 killed. 500 wounded. 600 captured.
- Dragonborn unharmed and ready to fight. Irileth capable of fighting and leading, but will be weaker in combat.
- 2,000 fighters return to Whiterun, 1,800 of which can fight immediately and bolster the defense.
- Siege capacity of the enemy seriously damaged.
- Three days of time of additional fortification of Whiterun walls, militia levying, etc bought. No word on when Solitude's forces will arrive, but presumably they will arrive soon.
Stormcloaks
- Moderate losses incurred. 3,800 killed. 800 wounded.
- Morale boosted from skirmish victory at Fellglow, at the cost of more fatigued men.
- Only two trebuchets remain. Siege will likely need improvised battering rams and ladders to take walls. Taking walls will be more costly in all likelihood.