Call your horse when you regain control and get ready for a long horse ride up past the mountains in the North region of the map (you can ignore riding with them and race on up ahead and reach the gate to speed things up significantly.
Once the gate is blown to smithereens, you’ll kick-start a huge battle against Dutch’s men! Use your rifle and plenty of cover to make your way up the hill, and take it easy as you’re not up against a time limit.
Once you’ve blasted your way past Dutch’s initial defences, follow the new yellow marker on the radar and shoot your way to the Gatling gun situated by the village. Man it and use its ferocious power to mow down all enemies that get in your firing line (look out for the explosive TNT crates dotted around the area too).
When all enemies are dealt with, you have to defend the soldiers who’re planting dynamite leading into Dutch’s stronghold. It won’t be an easy fight, so keep your rifle up and lay waste to the Indians that keep sticking their heads out of the walkways up above you.
Once they’re all killed, the gates will blow and you’ll now be in the camp and be on the last part of the mission. Dutch has manned a heavily protected Gatling Gun up high at the other end of the camp, your objective is to use your Sniper Rifle to shoot the two lamps that are hanging off the wooden poles behind him.
When they’re both shot down (remember to hide behind sufficient cover as you’re lining up your shots), Dutch will run off. Now you simply have to chase Dutch up the ladders and past various sections onto the mountain top itself.
There’s no real danger - apart from the fire - so as long as you stay away from it, you’ll eventually set off a cut-scene between you and Dutch, signalling the end of the mission, and the start of the ‘Home’ storyline.