Iron Nest Mission 6 Guide: Siege of Cartagena

Iron Nest Mission 6 Siege of Cartagena is the campaign’s first long multi-phase operation: break the encirclement’s command structure with chained measurements, deal with two coastal batteries that can come online at any moment, reduce the garrison, and then shepherd the breakout with fire and smoke. The mission warns you in advance that its measurements chain — and that its errors compound.

Quick Answer: Mission 6 Siege of Cartagena

• Verified on build/version: Source-checked 2026-09-12. The cited mission record does not publish a game build number, so no version is claimed here.
• Fixed rules: Three primary installations are concealed from aerial photography and located by chained measurements; spotter bearings carry up to 0.5° error and errors compound per chain link; two Vickers 580mm Coastal Batteries start offline and the Counter-Battery Timer begins when they come online; the breakout requires 8 additional enemy units destroyed, then the war horn; SMK smoke requests arrive with deadlines.
• Random or run-specific data: All grids, bearings, distances, and the coastal batteries’ activation timing come from the current operation.
• Starting resources: 300 requisition and 10 powder charges are listed in the mission record; the roster lists 8 entities with 1 armored target, so bring AP alongside HE.
• Gold conditions confirmed by the mission record: Measured Fire Star (ally kills ≤ 0), No Quarter Cross (kills ≥ 15), Unaided Fire Distinction (no aerial recon, kills > 18), Austere Service Medal (requisition spent ≤ 50).

1. Chain Your Measurements to the Three Installations

The three high-value targets — a relay, an assembly area, and the enemy commander — are concealed from aerial photography. Field intelligence locates them through a chain: distances from three spotters fix the relay; the assembly area hangs off the relay and a spotter bearing; the commander hangs off the relay and the assembly area.

The briefing states the trap verbatim: “Spotter bearings carry a margin of error of up to 0.5°. This mission relies on chained measurements; errors compound with each link in the chain.” A small error at the relay becomes a large error at the commander. Practical consequence: plot every link carefully, and when a solution looks off, re-check the earliest link first rather than re-measuring the last one.

2. Respect the Coastal Batteries

Two Vickers 580mm Coastal Batteries hold the cliffs over the harbour. They begin offline, and when they will come online is not known — the Counter-Battery Timer starts the moment they do. They must be destroyed before Cartagena can be called secure, so keep the requisition and the solve time to deal with them; do not spend everything on the three installations and leave the batteries for an empty magazine.

3. Eight More Kills, Then the Horn

Once the primary targets are confirmed destroyed, the next order requires 8 additional enemy units destroyed around the town. Only then do you sound the war horn for the breakout. Sounding it early is a documented mission failure: “You sounded the horn before the ground was clear.” A separate failure condition fires if enemy strength was not sufficiently reduced before the signal. Confirm the count first.

4. Answer the Smoke Calls

During the breakout, allied units call for support with deadlines: units pinned will request SMK shells on a stated grid, and the record shows a “requested before” timer on each call. Unanswered smoke gets troops killed in the open — the after-action message says so explicitly. Prepare SMK shells before the horn so the first request does not find an empty loading tray.

Mission 6 Medal Conditions

• Measured Fire Star: Gold with ally kills ≤ 0.
• No Quarter Cross: Gold with enemy kills ≥ 15.
• Unaided Fire Distinction: Gold with no aerial recon used and kills > 18.
• Austere Service Medal: Gold with requisition points spent ≤ 50.

Common Failures

• Trusting the end of a measurement chain. With up to 0.5° per bearing and compounding links, verify from the first link.
• Spending everything before the coastal batteries wake. They start offline, not absent.
• Sounding the horn before 8 confirmed kills. Both early-signal and insufficient-reduction failures are in the record.
• Answering smoke requests late or with the wrong shell. The calls carry deadlines, and unanswered smoke has a named failure message.
• Forgetting AP. One armored target is on the roster.

Sources / References

• Iron Nest DB — Siege of Cartagena mission record — Operation 6 resources, roster, chained installation fixes, the 0.5° compounding warning, coastal battery rules, breakout and smoke mechanics, and medal thresholds.

Update Log

• 2026-09-12: Published the source-checked Mission 6 walkthrough. All observation values remain run-specific; only the record’s stated rules are treated as fixed.

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