- This article is about an in-universe event. For the in-game mission, see Closure.
- "We can't let those nukes reach the battlefield and fuel more hate. I won't let it happen."
- ― Nagase
Blaze's recon operation from two days ago revealed that nuclear weapons from the Belkan War were being stored inside a mine at Mount Schirm and that they were being delivered to aggressor squadrons in Osea and Yuktobania. President Harling decided that in order to keep the Grey Men from delivering any more nukes, Razgriz Squadron would have to seal off the mine. 
After Razgriz Squadron arrived on the battlefield, they broke through enemy defenses and reached the mine. Even though they faced heavy resistance, they were able to seal off the mine by destroying the bedrock.
With the success of Operation Deepsix, the Grey Men would no longer be able to remove nukes from the mine. However, the OFS Kestrel lost track of the nuclear weapons that were already removed; as a result, they would have to continue their search for the missing nukes.