This is story related can't be missed. This is the 4th story in the campaign mode. You are apart of the Battle of Gallipoli, troops were landed by the British using Australian and New Zealand Army against the Ottoman Empire. You are tasked with moving up the beachhead and capture a flag. While being fired upon by mg nests and field guns. No problem.
The second part you are a runner. Their job was to run through the battlefield to get messages between positions on the battlefield. If you run all the way to the left of the map you will find the least resistance. You have to run to the forward position, then run back to where you started. Then run back to command position only to find out they bailed on you and are planning to bomb your position to cover the retreat. Great...Now you have to go back and tell everyone.
The third mission you are attacking a fort by yourself because... well why not. You make your way into the fort fighting to the top. Once everyone is dead and you claim the flag the mission is over.