Get on the horse and ride behind your comrade . When you'll reach the glade, turn left and travel through the wooden gate .Inside the fort, move in north-west direction and quietly get rid of the guard, who is hitting the Indian . Then free another one (he's under the wooden floor on the north, where are some enemies). You can find the last Indian on north-east. Form a group and wait until the soldiers, which are guarding the southern gate will go away. Approach from the back the last opponent and kill him quietly .Go through the gate and quietly follow Indians. Everything is going as was planned - just move behind your new comrades and eliminate some guard from time to time . After a while, you'll reach the iron bar. Soapy will take care of it . Walk inside the cave and fallow Indians.After leaving the cave, take the bow from the rock and kill the guards standing in front of you (when firing, remember to hold LPM for a while). Go up and take care of all enemies , who're defending the fort's entrance. Walk north and (with your comrade) steal two horses. Ride to Indians waiting near the road .Ride on the horse until you'll run into the wooden gate. Ram it (PPM). After entering the open area, help Indians in fighting off the enemy's attack . Try to always run - there're many opponents shooting all the time. After the fight, enter the camp  and simply wait for 'mission complete' info.
==After the Battle== After the battle at Hollister's Fort, a few remanents of the army remained, and continued to remain at the fort in the broken down barracks outside the main fort, due to the Blackfoot Indians seizing control of the fort. Colten can actually instruct the remaining soldiers, who are unarmed, to flee and hide, but the Indians will eventually catch up and kill the soldiers.