Reluctant Solitude is the squad story focused on Louffe and Stahlschrott. The combat mission in this is Scrap Metal Jacket. This squad story is only accessible in the postgame after both characters are unlocked.
This takes place on the same map as in Chapter 16: Forseti's Judgement. Differences are that only the northern half of the map is playable, with multiple grenadier shelters and indestructible walls scattered throughout.
Squad E will start in two positions: Louffe, Stahlschrott, and the Federation base camp will be on the lower ground in the NE corner of the map, while two others will start on the elevated position to their SW. The Imperial base camp is on the elevated position in the NW corner of the map. Because of the layout, no one from either the lower position or the higher position can directly access each others area, so only the people from the lower ground can capture the base camp.
Let's review the mission info, shall we?
"We'll need to take out the Imperial forces hiding around an island on the Crystal Sea. Due to the treacherous terrain, however, you won't be able to deploy any tanks."
Location: Snowbound Island
Description: Hunt down the enemies hiding on the island and capture their base camp. The mission fails if Stahlschrott or Louffe get iced.
"That should cover everything you need to know. Best of luck, Squad E."