Just as the Russian Navy fleet is being destroyed and the boarding party is leaving the AO, Overlord and Battle Captain notice unusual activity in the Oscar-II submarine while gathering the AAR (After-Action Report) on ISR (Intelligence, Surveillance and Reconnaissance). Further analysis shows that sailors on top of the sub are calling for some help from patrol boat crews to initiate a nuclear meltdown to destroy New York with them.
With that, Overlord and Battle Captain scramble to find an IRF (Immediate Response Force) in the area. Luckily, they are able to find one from DEVGRU (Naval Special Warfare Development Group).
Seven DEVGRU fireteams are en route to respond to distress signals from the USS Nimitz. Overlord redirects one of them to the sub: Trident Team, led by Lieutenant David Mason, codename: 'Section'.
Having observed only four sailors from the sub and two patrol boat crews enter, Overlord predicts that the interior is lightly defended. So he requests only one member from Trident Team to shut down the sub's reactor.
Section, armed with a TTI Benelli M4 shotgun, volunteers. Overlord approves, orders his UH-60 Blackhawk transport to drop him off, and gives the short version of the debrief.
Overlord: Trident 1, the Russians have rigged the sub to go nuclear. Find and render safe the reactor, over.
Section: Roger that, Overlord.
Blackhawk Main Pilot: Trident 1, this is your stop.
Section: Ready.
Trident 2: Give 'em hell, Section.
Section: You too, Harper, guys.
Section disembarks and engages two hostile sailors responding to his arrival. He sees the bridge's hatch rigged with a Thermite Charge trap.
But he sees it as a useless attempt by the Russians to kill more boarding parties, because he shoots/detonates it to breach the hatch. Now inside, he engages the responders in CQB (close quarters battle).
Then makes his way to the reactor, killing the sailors and patrol boat crews protecting its controls. Once clear, he gets on the switches and valves, stops the meltdown sequence, and sabotages the controls to prevent a reactivation.
Section: Overlord, this is Trident 1. Oscar-II's nuclear reactor is safe. I say again, the reactor is safe. Controls are sabotaged and unusable, over.
Overlord: Excellent work, Trident 1. Rendezvous with your teammates and get out of there.
Overlord calls the rest of Trident Team with their Blackhawk to extract Section. But then, Russian Army reinforcements arrive to respond to the sub crew's distress signal.
Overlord: Trident 1, we have you on ISR. You have multiple craft converging on your location.
Section: Roger, Overlord. Multiple hostiles fast roping down. Looks like they got engineers as well, over.
Overlord: Roger, Trident 1. Do whatever you can and hang in there. Extraction is 20 seconds out. Do you copy, over?
Section: Trident 1 copies all, over.
With engineer squads approaching, it seems the Russians are not giving up on the Oscar-II's nuclear reactor to bomb New York. So Section engages with everything he has.
The strategy is to close the gap quickly for the shotgun and FN Five-seven USG pistol. Section does this with ease, being an expert in CQB and extremely deadly with shotguns at close to medium range.
The operator clears the deck, then two more MI-17s move to the sub, so he prepares for another round. But a squadron of DAPs shoot down the Russian choppers and the rest of Trident Team arrive to extract their TL just in time.
