Hearts of Iron IV’s land war is won or lost in the Division Designer, a single screen in the Recruit & Deploy menu where you spend Army Experience to assemble battalions and support companies into reusable templates. The system looks simple, but the math behind it — averages for organization, sums for attack and defense, weighted formulas for armor and piercing — rewards players who understand which stats combine how. This guide walks through the official rules so you can design templates that fit your doctrine and theater rather than copying a streamer’s build blindly.

What changed

The Division Designer has been stable in its current shape since the No Step Back expansion reworked armored vehicles into the tank designer, but the core template rules the wiki documents remain the reference. A division is built from up to five combat regiments (the vertical columns) and up to five support companies. Each combat regiment holds up to five battalions — four at the start, raised to five once the relevant land doctrine is finished — for a hard ceiling of 25 line battalions per division. Support companies sit in a separate column and do not count toward combat width.

Every edit costs Army Experience. Adding, removing, or swapping a combat battalion costs 5 XP. Opening the first regiment of a new battalion category — infantry, mobile, or armored — costs 25 XP, which is why the wiki advises making your first battalion the category you will use most. Each support company added, replaced, or removed costs 10 XP. Duplicating a template, renaming it, changing its icon, changing its equipment assignment, or changing its priority (Reserves, Default, Elite) is free, so it costs nothing to experiment on a copy before committing.

How it works

Battalions and categories

Battalions are the front-line troops and the main source of most stats. They fall into three groups, and each regiment (column) may only hold battalions from one group:

  • Infantry battalions — Infantry, special forces (Mountaineers, Marines, Paratroopers), and towed line artillery/anti-air/anti-tank.
  • Mobile battalions — Cavalry, Motorized Infantry, Mechanized Infantry, and motorized variants of artillery, anti-air, anti-tank, plus rocket artillery and armored cars.
  • Armored battalions — Tanks, Tank Destroyers, and self-propelled artillery/anti-air, plus amphibious tanks.

Because there are five regiment columns but only three battalion groups, you never run out of columns; the real constraint is your XP budget and your production capacity, not the layout.

Combat width

Combat width is the room a division takes up at the front line, and it is the single most important sizing decision. Width is the sum of every battalion’s width: infantry and armored battalions use 2 width, artillery battalions use 3, and anti-tank/anti-air battalions use 1. Support companies add no width. The Mass Assault doctrine tree has nodes that reduce infantry battalion width, and the mountaineer special-forces doctrine can reduce mountaineer width.

The battlefield supplies a maximum width that varies by terrain, and extra width is added for each additional province the attack comes from. Certain combat tactics shift the battle’s width up or down. The wiki’s rule of thumb: field divisions whose width is a factor of the terrain’s combat width, so you fill the front without a penalty. Divisions that overflow the available width are sent to reserve and wait to reinforce. As a general guideline, smaller (roughly 20-width) divisions are better on defense because more of them can stack into a battle and recover organization, while larger (roughly 40-width) divisions concentrate attacks for breakthrough.

How stats combine

The combine rules are what trip up new players, because not everything adds:

  • Organization — the average across all battalions and companies. Adding a low-organization battalion (a tank or an artillery piece) can lower a division’s organization even though it raises other stats. Infantry and mobile infantry are the main organization donors; tanks and artillery are organization drains that you must buffer with enough infantry.
  • HP, soft/hard attack, defense, breakthrough — additive (summed). Doubling the template doubles these, but organization does not scale, so a bigger division is not twice as resilient.
  • Hardness — the average of the line battalions only (support companies excluded). It decides how incoming damage splits between soft and hard attack. Infantry are 0%, motorized ~20%, mechanized 60–75%, medium tanks ~90%, super-heavy 100%.
  • Armor — 40% × (highest battalion armor) + 60% × (average of all battalions and companies). A single very high-armor battalion lifts the floor; the average decides the ceiling.
  • Piercing — same 40/60 split as armor, using the highest piercing battalion or support company plus the weighted average. If your piercing exceeds the enemy’s armor, you get relevant combat bonuses; if their armor beats your piercing, they do.

The damage model reinforces these formulas: only about 10% of an attack roll counts for damage when the target still has defense to spend, but roughly 40% counts once the target’s defense is exhausted. An attack point that is not blocked is worth about four times a blocked one, which is why concentrated fire from a large division can drain an enemy’s defense faster than several small divisions.

Build path

Per doctrine

Your land doctrine tree tells you what your army is supposed to do, and your templates should match it.

  • Mobile Warfare / Superior Firepower offense leans on breakthrough and organization recovery. Front-load mobile and armored battalions, buffer them with motorized or mechanized infantry for organization, and keep the division fast. A 40-width medium-tank division with mechanized infantry can climb from the default 35% hardness to roughly 70%, dramatically reducing soft-attack damage.
  • Grand Battle Plan / Mass Mobilization defense wants cheap, high-organization infantry that holds width. Several 20-width infantry divisions with engineer and support artillery stack into a battle, recover organization, and contest every tile. Anti-tank support or a single line anti-tank battalion handles piercing against armored attackers.
  • Mass Assault reduces infantry battalion width, letting you cram more battalions into the same combat width — useful for manpower-rich, equipment-poor economies that want bodies on the line.

Per theater

Terrain changes which battalions suffer and which shine, so the wiki documents specific modifiers worth planning around:

  • Mountains and hills — Mountaineers are the first choice; lighter tanks penalize less than heavy ones; mobile battalions of all kinds take lower penalties; plain infantry only loses movement speed at worst.
  • Rivers — treated as half an amphibious assault, applied to movement too. Cavalry performs worse than baseline infantry across rivers, so do not lean on cavalry for river crossings.
  • Amphibious assaults (D-Day-style landings) — amphibious tanks and Marines lead, with amphibious tanks better than Marines, followed by baseline infantry. Artillery battalions take penalties proportional to weight; the Engineer Company gives a large bonus. Heavy tanks are a poor choice for naval invasions.
  • Forts — heavy tanks, the Engineer Company, and all artillery except anti-air give fort-attack bonuses; super-heavy tanks and super-heavy tank destroyers give the largest. The fortification mechanic already rolls these penalties in, so there is no separate penalty.
  • Low supply theaters — the Logistics Company reduces supply and fuel use for the whole division, valuable in the supply-poor eastern front or any long overland advance. Field Hospitals return a percentage of lost manpower (trickleback) and reduce experience loss, worth it for front-line divisions you intend to keep alive. Maintenance Companies add reliability, cutting equipment losses in combat and training — advised for any division fielding expensive gear like tanks.

Support company picks

Up to five support companies, one of each type, no width cost. The wiki groups them by role:

  • Engineer Company — +2 max entrenchment plus terrain attack/defense and river/fort bonuses; near-mandatory for line-holding infantry.
  • Support Artillery / Support Anti-Air / Support Anti-Tank — cheaper, lower-stat versions of the line battalion that do not slow the division or affect paradrops. Use them to add capability to fast divisions where a towed line battalion would cap speed at 4 kph.
  • Recon companies (Cavalry, Motorized, Armored Car, Light Tank) — raise the Reconnaissance stat, making it easier to counter enemy combat tactics, and give terrain movement bonuses. They do affect division speed, so pick the one whose speed matches your division.
  • Signal Company — raises Initiative, speeding planning and increasing reinforcement chance from reserve; strong for attacking divisions.
  • Military Police — boosts Suppression for partisan control; pair with 2–6 cavalry battalions for an efficient rear-area garrison.
  • Maintenance Company — reliability bonus, advised for expensive equipment.
  • Field Hospital — trickleback and reduced experience loss, advised for front-line divisions.
  • Logistics Company — reduces supply and fuel use, essential in low-supply theaters.

Sizing rule of thumb

The wiki’s summary, repeated because it is the most cited guideline: 20-width divisions are generally better at defense, 40-width at attack. Keep a breakthrough army of large divisions and several standard-size divisions for holding the line. Composition makes or breaks this — a 40-width pile of tanks with no organization buffer will collapse the moment it meets prepared defense.

What it means

Templates are not a one-time decision. The wiki notes that most countries start with suboptimal single-battalion infantry templates, and that the sensible play is to keep a copy of the original so you can iterate from it without paying XP twice. As Army Experience, manpower, and equipment accrue, you fold in better battalions and support companies, reassign divisions to the upgraded template on a rolling basis, and prioritize which templates get the newest equipment through the Reserves/Default/Elite tags and the Division Equipment menu.

The single most common mistake is treating a division as a stat pile rather than a system. Organization is an average, so every tank and gun you add dilutes it unless you also add infantry or mobile infantry to compensate. Armor and piercing use the 40/60 highest-plus-average formula, so one strong battalion and a high average baseline (mechanized infantry) do more than two mismatched ones. And because width is a sum that must divide the terrain’s capacity, a template that is brilliant on one front can fight under penalty on another. Design per doctrine and per theater, duplicate before you edit, and the Division Designer stops being a guessing game.