Hearts of Iron IV Open Beta Update 3.03 Reworks Armor, Doctrines, and Reliability

It also improves math precision for extreme values and fixes convoy efficiency when one admiral manages 33 or more regions but covers only 1.

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Hearts of Iron IV Open Beta SE Update 3.0 artwork showing four military leaders over a world map

Hearts of Iron IV Open Beta SE™ Update 3.03 is now available with a fresh round of experimental armor changes, doctrine adjustments, tank module tuning, and unit stat updates. The branch is running as Operation Postern v1.19.2.0.3eb1 (85f4), and its features may still be changed or removed before they reach the main game.

Zwirbaum, a game designer for Hearts of Iron, also asked beta players to test how these changes play together. The Steam announcement says feedback will help the team judge the experimental systems, while a small core technology fix improves precision for very small and very large values in exponent, logarithm, and power calculations.

For players following the beta’s earlier technical pass, Update 3.03 comes after the previous performance update, which changed threading libraries for some newer CPU setups. This release turns back toward battlefield systems, with armor chassis, reliability, doctrines, and support units all receiving changes.

How to join the Hearts of Iron IV Open Beta

To try the branch, open the game in your library and follow these steps:

Right-click Hearts of Iron IV in your library.
Select Properties from the menu.
Open Game Versions & Betas.
Choose the beta branch called open_beta.

Anyone already using the Open Beta client should receive the update automatically. Issues should be submitted through the Hearts of Iron IV bug report forum, along with the version being used.

Hearts of Iron IV Open Beta SE™ Update 3.03 Patch Notes

The biggest changes target armored equipment. Chassis can now modify module bonuses, reliability can feed into selected stats, and several tank variants have more defined battlefield roles. Land doctrines, air doctrine, special projects, modules, unit stats, and modding math also receive adjustments.

Experimental Feature: Equipment can now have defined multipliers to the ‘additive stats’ from the modules, and multipliers to the ‘multiplicative stats’. This can be done on selective stats, e.g. only to Soft Attack, or done on the entirety of the stats, and with defined intensity, e.g. +5% Soft Attack bonus to all modules installed on this specific tank chassis. This is experimental change, and is not guaranteed to stay, so modders before you start going crazy over this, be aware that this change can be reverted. This change is not localized, so it will be properly displayed only in English.

Interwar Light, Medium and Heavy Tank Chassis gets -5% Soft, Hard and Air Attack bonus for module additive values.
Improved and Advanced Light, Medium and Heavy Tank Chassis get respectively +5% and +10% Soft, Hard and Air Attack bonus for module additive values. (5% for the Improved and 10% for the Advanced)
Modern Tank Chassis gets +12.5% Soft, Hard, Air Attack bonus for module additive values.

Developer Commentary: With last open betas updates there was a focus on reducing the power gap on the specialized armor variants, now with this change I want to experiment and address that there is a feeling of armored units being on underpowered side – providing power boost, as well as increasing and providing incentive into researching, and fielding higher tiers of the armored equipment instead of just sticking to the most basic tank chassis. This may also due to various tiers of equipment coming ‘online’ at different timeframes, may also provide some extra incentives of considering different tank types. (e.g. Light Tanks may get its moment of glory for longer). I have seen some alternative suggestions about limiting to what modules can be installed over on which tank chassis level (e.g. no Improved Medium Cannon on Interwar Medium Tank) – it would require doing a big pass on the modules, their tech availability, where something is unlocked and then finally doing UI/UX changes to mention that this specific module can’t fit on a said chassis and why.

Experimental Feature: Equipment can now have defined stats that scale with the reliability stat of the equipment. This new effect is clamped between 0 and 1, where 0% reliability provides 0% stats defined in that new stat block, while having 100% reliability provides 100% of the stats defined in that new stat block. Following stats should not be used in it: Reliability, Reliability Factor, Carrier Deck Size and IC Cost. This is experimental change, and is not guaranteed to stay, so modders before you start going crazy over this, be aware that this change can be reverted. This change is not localized, so it will be properly displayed only in English.

All Tank Chassis except for Land Cruisers have defined 0.5 HP scaled by reliability. For 100%+ Reliability tanks it should increase the HP of Light/Medium/Heavy/Amphibious/Super Heavy Armor to 3.5 HP from 2 HP.
Line Tank Destroyers, Self-Propelled Anti-Air, Self-Propelled Artillery HP reduced from 0.6 to 0.5. For 100%+ Reliability armor variants it should increase its HP to 1.25 from previous 0.6 HP
Regimental Support Tank Destroyers and Self-Propelled Anti-Air HP reduced from 0.2 to 0.1. For 100%+ Reliability armor variants it should increase its HP to 0.65 from previous 0.2 HP

Developer Commentary: This experimental change is aiming at further increasing the incentive of researching higher tiers of tanks and armored units, and also giving some benefits to Reliability. This change should make armored units a bit more efficient in the long run, and designs that are a bit less ‘skewed’ towards ignoring reliability should end up benefiting a bit more from this change. Math for how HP are calculated per unit basis are a bit less straightforward, than just being multiplicative or additive, but numbers chosen were adapted for the calculation. Anything that increases HP of subunits will have stronger effect due to it, but those picks previously were not that often used, which should increase their competitiveness

Tank Destroyers, Self-Propelled Anti-Air, Self-Propelled Artillery – Breakthrough penalty standardized and set to -75% regardless of ‘weight’
Regimental Tank Destroyers and Regimental Self-Propelled Anti-Air – Breakthrough penalty standardized and set to -90% regardless of ‘weight’
Tank Destroyers and Self-Propelled Artillery – Now have a defense bonus of 25%, standardized regardless of ‘weight’
Regimental Tank Destroyers – Defense penalty reduced to -33%, standardized regardless of ‘weight’

Developer Commentary: In order to provide a bit more distinct roles for Tank Destroyers, Self-Propelled Anti-Air and Self-Propelled Artillery, we have now standardized and lowered breakthrough stat they provide, so that they no longer serve as ‘Tank Replacement’, but rather as it should be, specialized variant for their specific role. Self-Propelled Artillery and Tank Destroyer units.

Land Doctrines

Large Unit Tactics Adoption Bonus: Supply Reduction switched from All Infantry, Mot & Mech to Leg Infantry
Large Unit Tactics Reward 4: Switched Bonus from applying to All Infantry, Mot & Mech to Leg Infantry

Developer Commentary: Large Unit Tactics has been unquestionable king of the Infantry Subdoctrines. With this change, the aim is to keep its benefits and rewards centered around Leg Infantry and the general theme of the ‘Infantry Mass Offensives’ while lowering some of their potential for Mechanized and Motorized infantry.

Mobile Infantry Reward 2: Added +10% Soft Attack Bonus to All Infantry, Mot & Mech
Mobile Infantry Reward 4: Soft Attack bonus removed and added +10% Breakthrough bonus to Motorized & Mechanized Infantry
Mobile Warfare Armor Milestone: Now also grants +15% Breakthrough Bonus to Army
Mass Assault Operations Milestone: Now grants -10% Minimum Training Level from previous -5%
Mass Assault Artillery & Combat Support Milestone: Minimum Training Level -5% was replaced with Reinforce Rate +2%

AIR DOCTRINES:

Strategic Destruction Fighter Milestone: Bonus to Interception Mission Efficiency lowered to +15%

SPECIAL PROJECTS:

Proximity Fuzes bonus to Naval AA reduced to +15%:

TANK MODULES:

Rocket Launcher: Breakthrough increased from -2 to 4; Added Defense of 4; Increased Hard Attack to 4
Improved Rocket Launcher: Breakthrough increased from -2 to 8; Added Defense of 8; Increased Hard Attack to 6
Anti-Air 2: Air Attack reduced from 32 to 30
Anti-Air 3: Air Attack reduced from 46 to 42
Easy Maintenance: IC cost reduction reduced from -7.5% to -5%, and XP cost reduced from 30 to 20. Reliability Bonus reduced to 7.5%

Developer Commentary: This module has been a guaranteed pick before in most of the circumstances, especially due to the nature of stacking cost reducing modifiers being more effective the more you have. As right now Reliability has some potentially extra effect, and armored equipment should suffer lower losses, this could result in an ever increasing amount of armored equipment present at any time. We will likely look into addressing other cost reductions from other sources in the future.

Cast Armor: Now also provides +10% HP
Sloped Armor: Now also provides +5% HP
Welded Armor: Now also provides +5% HP
Auto-Loader: Now also provides +2% Soft Attack and +2% Air Attack
Stabilizer: Now also provides +4% Hard Attack
Smoke Launchers: Breakthrough increased to 2 from 1
Extra Ammunition Storage: Increased Defense to 5 and Breakthrough to 3.

LAND UNITS:

Bicycle Infantry Support Equipment Requirements lowered to 5 from 10
:Motorized Infantry HP increased to 27.5
Mechanized Infantry Soft Attack Bonus of +10% Removed
Amphibious Mechanized Infantry Soft Attack Bonus of +10% Removed
Cavalry now have breakthrough bonus of +20%
Artillery, Motorized Artillery, Rocket, Motorized Rocket, Truck-Drawn Rocket, Anti-Tank, Anti-Air, Motorized Anti-Tank and Motorized Anti-Air HP increased to 1.6

TECHNOLOGIES:

Improved Infantry Equipment I and II now provides +10% Soft Attack Bonus to Motorized & Mech Infantry Category from previous +5%:

BUG FIXES:

Reverted: “Fixed Superstructures now also prevent from putting one category bigger guns on the Amphibious Tanks.”.
Developer Commentary: This change was causing another issue, so for the time being it is being reverted. It may get re-added after we will get it fixed and sort some potential issues with it.
Trade Interdiction Submarine Milestone Submarine Attack +0.1 got replaced with Submarine: Torpedo Attack +10%
Marine Commando: Reward 5: Pioneers should now provide proper +15% Armor bonus to the Amphibious Armor
Fixed an OOS (mods only), that could occur if very large numbers were used.

MODDING:

Improved precision for the exp, log, and pow (power) functions.

How do these armor and doctrine changes feel in your campaigns? Share your thoughts in the comments, and follow us on X, Bluesky, YouTube, Instagram, Steam, and Telegram for more coverage.

Hearts of Iron is the first ever World War II PC game of true Grand Strategic scope. The game map spans the entire world and allows players to take part in any front they choose. You can play any nation in the world, but the game focuses on the epic struggle between the great alliances of the world orders - Fascism, Communism and Democracy.