The script for this Paralogue can be found here.
The army starts off in a small enclosed space with 7 openings into the building. There are 5 NPC villagers inside and, depending on how many survive the chapter, more items will be given once the chapter is completed. Brady will join the army once Chrom or Maribelle talks to him.
These are the possible items to attain:
The chapter's boss drops a Master Seal.
Unlock and Access
This paralogue will unlock once Maribelle achieves an S-Support with someone and Chapter 13 has been completed. It cannot be accessed directly from a chapter until Chapter 16. However it can be accessed earlier only if the following Paralogues have been unlocked as well: