How many missions are in IRON NEST?

Fifteen. Steam's achievement list shows fourteen numbered operations each with its own completion achievement, plus the finale, White Shells, whose outcome is recorded by the four ending achievements instead. Fan sites claiming seventeen operations do not match the game's own achievement data.

What is mission 3 in IRON NEST?

Liberation. It is where multiple target sets start arriving faster than you can lay the gun, which is why charge planning begins to matter here.

What is the hardest mission in IRON NEST?

By completion rate, Counter-Battery is the wall: it is cleared by 50% of owners against 69.7% for the mission before it, the largest single drop in the campaign. The lowest completion rates belong to the late missions, with Final Harvest at 3.4%.

Campaign

All 15 IRON NEST missions

The campaign in order, what each operation actually asks of you, and — because Steam publishes it — the share of players who clear each one. That last column is the most honest difficulty rating available for any game.

The IRON NEST campaign map room: a large wall map of Spain marked with regional borders and front lines, flanked by mission boards and lit by hooded green lamps. — The campaign map. Fifteen operations across an alternate-history Spain, from a calibration shoot to the four endings of White Shells. Screenshot: IRON NEST: Heavy Turret Simulator.

Fifteen operations, not seventeen

Several IRON NEST fan sites state the campaign is seventeen operations long. The game's own achievement list shows fourteen numbered operations, each with a completion achievement, plus the finale White Shells, which has no single completion unlock because the four ending achievements record it instead. We follow the achievement list.

Completion percentages are global Steam achievement unlock rates, read on 2026-08-10. They are shares of everyone who *owns* the game, so they fall steeply through the campaign regardless of difficulty — what matters is the size of each drop.
#	Operation	What it asks	Cleared by	All gold
1	Calibration FireReading the map grid Elevation and charges	The tutorial shoot. Read a grid reference off the teleprinter, measure it on the map, set bearing and elevation, fire.	92.5%	72.2%
2	Fire and LightShell types	Introduces STAR shells. You light an area first, then engage what the light reveals.	83.9%	82.4%
3	LiberationElevation and charges Ballistic calculator	The mission most people mean when they search for "mission 3". Multiple target sets arrive faster than you can lay the gun, so charge planning starts to matter.	69.7%	0.1%
4	Counter-BatteryTriangulation Recon planes	The campaign’s first real wall — half of all players stop here. Enemy guns shoot back, and you have to find them before they range you in.	50%	0.3%
5	Iron RoadBallistic calculator	A railway interdiction. The target is moving on a known line, so you are solving for time-of-flight rather than for position.	36.7%	0.1%
6	Siege of CartagenaShell types	Long-range support fire with friendly troops close to the impact area, which restricts which shells you can safely use.	24.1%	0.1%
7	The GorgeElevation and charges	A defensive engagement in tight terrain. Elevation is constrained by the gorge walls, so charge selection does the work instead.	19.5%	0.4%
8	Rock of GibraltarElevation and charges	Maximum-range work against a fortified position. Expect to be firing at or near six charges for most of the operation.	17.4%	0.1%
9	Dead ReckoningTriangulation Shell types	The primary targets do not appear through normal reconnaissance. You narrow each one to a suspected area from the written reports, then confirm it before spending a destructive shell on it.	14.3%	0.1%
10	Fire on CallBallistic calculator	Reactive fire missions arrive continuously. The bottleneck is how fast you can convert a call into a laid gun, not whether you can do the maths at all.	11%	0.8%
11	High TideBallistic calculator	Coastal defence against a landing. Targets are moving on the water and closing.	7.1%	0.4%
12	Blind FireTriangulation	Fire missions with the observation network degraded. You are working almost entirely from written reports.	6.3%	0.1%
13	Phantom BatteryRecon planes Triangulation	The most-discussed mission on the Steam forum. Some of what the reports point you at is not really there.	4.6%	0.1%
14	Final HarvestShell types	A night operation. Illumination is a resource you have to budget like any other.	3.4%	0.1%
15	White ShellsAll four endings	The finale, and the only mission where your decision changes the outcome. All four endings branch from here. Derived by summing the four ending achievements. Players who replay the finale for a different ending are counted more than once, so the true share of finishers is somewhat lower.	7.6%*	0.1%

Where the campaign actually stops people

The steepest fall in the whole campaign is between Liberation and Counter-Battery: 69.7% down to 50%, a loss of 19.7 points. That is where the enemy starts shooting back, and it is the single most useful thing to know before you buy the game. It has its own walkthrough.

After that the curve keeps falling but never that sharply again — each late mission sheds a few more percent, which reads as attrition rather than a wall. Only about 3 in 100 owners reach Final Harvest, and roughly the same share see any ending at all.

The gold-medal column tells a different story. Gold on the first two operations is nearly universal, and then it collapses to a tenth of a percent almost everywhere else. Gold is not a slightly harder version of clearing a mission; it is a separate discipline built on doing the map work fast enough to never waste a round.

What you need before each stage

The campaign introduces mechanics in a deliberate order, and each mission's row above links to the pages covering what it leans on. In broad strokes:

Missions 1–3 teach the loop: read the grid, convert range to elevation, load, fire.
Mission 4 adds an enemy that ranges you in, which makes triangulation and reconnaissance load-bearing rather than optional.
Missions 5–8 stress charge selection: moving targets, restricted arcs, and maximum-range work.
Missions 9–14 take away information. Targets stop appearing on reconnaissance, observation degrades, and reports start being wrong on purpose. The probe-round technique matters more than accuracy here.
Mission 15 asks what you are willing to do. See endings.

Challenge Mode

The campaign is roughly 8–12 hours for a single pass. Replayability is meant to come from Challenge Missions, which vary procedurally and record your best single-run score after the mission is completed and the newspaper dismissed. Ties break on time. Chill Mode instead accumulates kills across runs, so it is the mode to use when you are practising the map work rather than chasing a leaderboard.

Walkthroughs

Two operations have enough people stuck on them to warrant their own page. The rest are covered by the mechanics guides linked in each row — if a mission is giving you trouble, it is nearly always one specific mechanic rather than the mission as a whole.

Counter-Battery — finding guns that are firing at you, and whether repositioning helps.
Phantom Battery — the most-discussed mission on the Steam forum.

Sources

Global achievement stats, Steam — The authoritative mission list and the completion percentages used for the difficulty ranking.
Official FAQ thread, Steam Community — Maintained by the developers. First-party answers on platforms, pricing, multiplayer, VR and design intent.
General Discussions, Steam Community — Player reports on mission behaviour, including the counter-battery respawn rules.

Last updated 2026-08-10.