This guide will give you a quick overview of the Art and the Dead Letter locations for 2 achievements in the Cultural Property mission in the new Art of War DLC

After the mission start, move on until you get tasked to take out the enemy sniper. Keep moving north east, until you reached two pinned down FIA soldiers. Take out the sniper by either shooting him yourself, or calling in its position. Once it's safe, move left around the house and into the small house behind it.

After dealing with the sniper, follow the road to the east. At the T-junction, you will see a small chapel to the right. There will be a single AAF soldier defending it, and he will set off a Mine-Dispenser and a smoke grenade. Take out the soldier and carefully move into the chapel to find a letter on the floor.

From the chapel, move straight north until you reach the edge of the town. You should see a helicopter crash site. The art is in the building next to it.

Before you get the third art piece, I advice you to deal with the malfunctioning UGV at the gas station first. Once you've destroyed the UGV, move to the alley north of the building where you can find the UGV operator. The third artpiece is in a small brown building in that alley.

From the third artpiece, move to the north west, and follow the road. You should find 2 containers to the left side of the road. The fourth artpiece is located in the blue container

The final artpiece can be found just south of the camp with the hostage. First deal with the convoy, and get the final artpiece before clearing the camp.