The mission will begin with an attack on a convoy. Pick up the rifle from the roof with the interaction button and use it to shoot one of the soldiers on the street. Afterwards you can jump down and get rid of the others together with your companions.
With the last enemy dead, you will take control of the carriage.
Your task now will only be to press the Assassins Guild button at the right time to get rid of the British soldiers guarding the road.
Optional objective: Find and kill the general.
Optional objective: Perform stealth assassinations from a corner spot - 3.
After a short ride you will eventually reach the enemy camp, where prisoners are held. Your main mission is rescuing them while not letting the guards notice you. You will also receive two additional objectives: kill the general marked on the map and assassinate three soldiers from behind a corner.
Firstly take care of the general. He can be found to the right of the camp entrance.
He's walking beside the stocks, nearby the stone wall.
Sneak in there from the side and observe the enemy's walking pattern. As he moves away from the prisoner, assassinate the soldier building stocks and hide behind a pile of crate nearby. From there you will be able to kill the general, but only after a big group of soldiers return to their position.
After eliminating him, head back to the camp entrance. From there you should approach the first prisoner on the left and hide in the bushes beside a pile of crates.
The guard guarding the Indians will pass beside the crates and stop for a moment. Use that time to hide behind the crates, whistle and kill the enemy.
With the man dead, free the prisoners.
Right after opening the first stocks, you need to quickly run to the end of the stone wall of the left.
If you're fast enough, you should get there before the next guard shows up there. When the enemy approached the wall, kill him with a hidden blade.
The next group of prisoners are held on the ship. In order to save them, swim to the other side of the boat and grab onto it where one of the soldiers is. You will be able to quickly kill him and drop into the water below.
After he's dead, go lower and wait for the second guard to return to his position.
Board the ship and hide behind the cargo. Whistle from there and get rid of him to save the Indians.
The last group of prisoners can be found nearby the first. Approach them from the left, going between tents and bushes and wait for the guard to leave. That way you will be able to finish this part of the mission.
After a short cutscene you will be attack by British soldiers. Don't try to fight them now, instead keep pressing the jump button to grab the nearest enemy and block the rifle shots with his body.
Optional objective: Avoid firing line damage.
Optional objective: Completed all the constraints in one playthrough.
Now your main task will be killing Silas, who's hiding inside the fort. It's not all that difficult, as you just have to run to the map (he's marked on the map) and stick a hidden blade in his stomach to end the mission. You don't need to worry about the enemies you come across on your way.
Things will be more difficult if you decide to complete the additional objective of avoiding any enemy fire. To complete it, after killing the first enemy you have to quickly run to the group of soldiers waiting for you by the fort entrance.
You need to use one of them (by pressing the jump button) to block the attack of the riflemen line standing in the gate. Afterwards quickly attack the enemies.
Fight with them just for a couple seconds so that they stop reloading their guns and afterwards immediately run up the stairs on the left to reach Silas. Kill the enemy with a counterattack to end the sequence.