Operation Iron Citadel is a DMZ story mission in Call of Duty: Modern Warfare 4, set at Chang-san Air Base in North Korea. The base carries a THREAT: CRITICAL rating, and it chains a keycard hunt, a code puzzle, a boss fight and a demolition job into one long run that ends on an exfil chopper.
Quick answer: Find and upgrade the access card, open the bunker armory with a six-digit code, kill Commander Colossus, grab the manifest, mine the armory and three strike aircraft, capture the SAM site, then exfil.
Operation Iron Citadel objectives in order
The mission select card shows [THREAT ASSESSMENT: CRITICAL], recommends a 3-Plate Armor Vest, Medkit and Ammo Box, and lists the main objectives Infiltrate the Base, Recon Armory Ordnance and Disrupt the Operation. In the field, the HUD splits them into 14 lines under “MISSION: OPERATION IRON CITADEL”. Each one clears before the next appears.
| # | Objective | Where |
|---|---|---|
| 1 | Approach the Air Base | North Korean Wilderness |
| 2 | Infiltrate the Air Base | Chang-san Air Base |
| 3 | Search for an Access Card (out of 4) | Base buildings |
| 4 | Pick Up the Access Card | Building the scan marks |
| 5 | Upgrade the Access Card | Admin Complex No. 2 |
| 6 | Find the Armory Doors | Chang-san Air Base Bunker |
| 7 | Find the Armory Keycode (out of 3) | Bunker rooms |
| 8 | Explore the Armory | Armory |
| 9 | Collect the Armory Manifest | Armory rooms |
| 10 | Standby for Instruction | Armory |
| 11 | Plant Explosives in the Armory | Munitions crates |
| 12 | Plant Explosives on the Strike Aircraft (0/3) | Hangar and outside |
| 13 | Capture the SAM Site | Air base |
| 14 | Exfil the Armory Manifest | Exfil chopper |
The air base is rated THREAT: CRITICAL, while Admin Complex No. 2, the bunker, and its rooms are rated THREAT: EXTREME. Pack plenty of armor plates. An Armor Box or Ammo Box helps keep the squad supplied through the long firefights.
How to find the access card at Chang-san Air Base
You infil in the North Korean Wilderness and make for the base. The banner NORTH KOREA / CHANG-SAN AIR BASE / THREAT: CRITICAL marks your arrival. A SAM site outside the perimeter wall offers a CAPTURE SAM SITE side op; stand inside it until the CAPTURE TIME bar fills to clear it.
The doors inside the base sit behind card readers that show “UNLOCKS VIA CARD READER – LOCKED” and “NO AIRBASE ACCESS CARD IN INVENTORY”. You do not search bodies for the card; your handler scans buildings for it instead.
Upgrade the access card in Admin Complex No. 2
You now carry the AIR BASE ARMORY CARD – SINGLE USE, a legendary key described as “Unlocks Armory in Chang-san Air Base in North Korea.”
Armory doors and the armory keycode
An enemy helicopter arrives outside the admin building and deploys reinforcements; bring it down or take cover. Next, enter the CHANG-SAN AIR BASE BUNKER by way of the Entrance Garage, rated THREAT: EXTREME. The COMMANDER COLOSSUS / ENTRANCE GARAGE banner appears there, where soldiers are defending the garage.
Go along the corridor to the Armory entrance, marked by red trim and an “OFFICERS ONLY” sign. Its keypad shows “ENTER ACCESS CODE” (F on PC).
A six-digit code is assembled from three note fragments hidden around the bunker. Each discovery adds to the HUD’s “Known Digits” line and advances the counter toward 3. In the medical wing, check a desk for the TRANSFER SLIP – DO NOT FILE. It says “Armory access code fragment” and “Second Segment: 28”, with Lt. Bale’s sign-off. The digits on the slips change between matches, so use the numbers from your own notes, not a code from another match. Another fragment can be in the bunker’s Control Room.
Have the squad search different bunker offices and rooms for the remaining fragments. After the “Known Digits” line contains all six numbers and the counter reaches 3/3, head back to the keypad and input the digits in sequence.
Commander Colossus fight and the armory manifest
Once the armory door swings open, Commander Colossus moves in from the distant end of the lengthy bunker corridor near the armory, firing a heavy automatic weapon. Use the corridor doorframe for cover: peek out with a scoped rifle, target his head, then retreat to reload. He can also be waiting inside The Armory itself while Collect the Armory Manifest is active.
Defeating him awards 1198 XP and registers “ELIMINATED ARMORED COMMANDER”. He drops DETONATORS and Nitro Compounds.
Search the armory rooms for the Armory Manifest. Picking it up advances the mission to Standby for Instruction, which clears after a few seconds.
Plant explosives in the armory and on the strike aircraft
Capture the SAM site and exfil the armory manifest
Push through to the base SAM site and remain there until the CAPTURE TIME bar completes. During this objective a MILBASE ALARM: ACTIVE warning can appear (“Soldiers are on high alert due to hostile activity in the area”), so expect more soldiers. The cleared objective displays “SIDE OP COMPLETE / CAPTURE SAM SITE”. Nearby care packages have the prompt “HOLD TO OPEN CARE PACKAGE”.
Next, “EXFIL HELICOPTER INBOUND” shows, and the chopper comes down by the base fence. Enemies keep shooting at the chopper as you wait, so stay in cover until it touches down, then board with the manifest.
Aboard the helicopter, look for MISSION COMPLETE / STORY MISSION to confirm the mission has ended; “EXFIL DEPARTING” appears during takeoff. The following screen displays EXTRACTION SUCCESSFUL.
Operation Iron Citadel rewards
| Extraction summary line | Amount |
|---|---|
| Story Mission Payout | 5,000 |
| 3 Side Ops Payout | 1,500 |
| Cash Banked | 1,150 |
| BANKED CASH | 7,650 |
The mission select card lists a key (its name is cut off on the card), an LTV and 25000 as rewards.
