This takes place on the same map as the third one in Chapter 4: The Battle of Siegval. This time, the far east and southwest parts of the map are inaccessible, with barricades blocking access to these.
Zaiga, Vancey, and the Federation base camp will start in the SE corner of the map on the elevated section, while Gertrude will start in the NE corner surrounded by enemy troops.
Here are your orders
"The advance party was ambushed from behind and cut off from the main force. There are good soldiers out there, alone. They need backup, and they need it now. We'll deploy Shocktroopers to hit hard and get our allies out fast.
Location: Siegval Line, Cliffside Summit
Description: Save the advance party and eliminate all enemies. The mission will fail if Zaiga, Vancey, or Gertrude is killed.
"That concludes the briefing. Now send in the cavalry!"
If there is at least one enemy infantry unit who can see Gertrude during enemy phase, other enemies (scouts and shocktroopers) will likely run towards her position.
This can get overwhelming considering she has limited ammunition
If only the enemy pillboxes (as opposed to infantry) can see her, then a shocktrooper who initially hides in grass will come out of hiding and run towards her position, while most other enemies will ignore her.
This can be useful if Gertrude's ammunition usage is planned right
If none of the enemies see Gertrude, none of the enemies will run towards her position