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Hearts of Iron IV
Hearts of Iron IV
3.03|Aug 28, 2026
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HOI IV | Open Beta SE™ Update 3.03

3/5 Moderate

BETAMajor tank chassis overhaul introduces stat scaling based on reliability and chassis tier, alongside significant rebalancing of land doctrines and motorized units.

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Key Changes

  • 1Experimental feature: Equipment HP now scales with Reliability (100% reliability grants max HP)
  • 2Experimental feature: Tank Chassis now provide stat multipliers based on tier (Modern/Advanced get buffs, Interwar gets nerfs)
  • 3Large Unit Tactics doctrine nerfed: Supply reduction now only applies to Leg Infantry
  • 4Mobile Warfare doctrine buffed: Now grants +15% Breakthrough bonus to the entire Army
  • 5Motorized Infantry HP increased to 27.5 and Cavalry gained +20% Breakthrough
  • 6Mechanized Infantry Soft Attack bonus of +10% has been removed
  • 7Easy Maintenance module nerfed: IC cost reduction lowered to -5% and Reliability bonus lowered to 7.5%
  • 8Base HP increased to 1.6 for all Artillery, Anti-Tank, and Anti-Air units
  • 9Rocket Launcher modules significantly buffed with increased Breakthrough, Defense, and Hard Attack
  • 10Fixed computational errors for exponents and logarithms affecting high-region naval efficiency

All Changes

🚜Tank Chassis(16)

  • newTank Chassis: Introduced experimental multipliers for additive and multiplicative module stats based on chassis tier.
  • nerfInterwar Tank Chassis: Interwar Light, Medium, and Heavy Tank Chassis now receive a -5% penalty to Soft, Hard, and Air Attack module additive values.
  • buffImproved Tank Chassis: Improved Light, Medium, and Heavy Tank Chassis now receive a +5% bonus to Soft, Hard, and Air Attack module additive values.
  • buffAdvanced Tank Chassis: Advanced Light, Medium, and Heavy Tank Chassis now receive a +10% bonus to Soft, Hard, and Air Attack module additive values.
  • buffModern Tank Chassis: Modern Tank Chassis now receives a +12.5% bonus to Soft, Hard, and Air Attack module additive values.
  • newReliability Scaling: Introduced experimental stat scaling where equipment HP is determined by Reliability (0% to 100%+).
  • buffTank Chassis: All Tank Chassis (except Land Cruisers) now have 0.5 HP scaled by reliability; 100% reliability increases HP from 2 to 3.5.
  • changeTank Variants: Line Tank Destroyers, SPAA, and SPART base HP reduced from 0.6 to 0.5, but scales to 1.25 HP at 100% reliability.
  • changeRegimental Support Variants: Regimental Support Tank Destroyers and SPAA base HP reduced from 0.2 to 0.1, but scales to 0.65 HP at 100% reliability.
  • changeTank Destroyers: Breakthrough penalty standardized to -75% regardless of weight.
  • changeSelf-Propelled Anti-Air: Breakthrough penalty standardized to -75% regardless of weight.
  • changeSelf-Propelled Artillery: Breakthrough penalty standardized to -75% regardless of weight.
  • changeRegimental Tank Variants: Regimental Tank Destroyers and SPAA breakthrough penalty standardized to -90%.
  • buffTank Destroyers: Defense bonus increased to 25% (standardized).
  • buffSelf-Propelled Artillery: Defense bonus increased to 25% (standardized).
  • buffRegimental Tank Destroyers: Defense penalty reduced to -33% (standardized).

🎖️Land Doctrines(7)

  • nerfLarge Unit Tactics: Supply Reduction bonus now only applies to Leg Infantry instead of All Infantry, Motorized, and Mechanized.
  • nerfLarge Unit Tactics: Reward 4 bonus now only applies to Leg Infantry instead of All Infantry, Motorized, and Mechanized.
  • buffMobile Infantry: Added +10% Soft Attack bonus to All Infantry, Motorized, and Mechanized.
  • changeMobile Infantry: Soft Attack bonus removed and replaced with +10% Breakthrough bonus for Motorized and Mechanized Infantry.
  • buffMobile Warfare: Now grants +15% Breakthrough bonus to the entire Army.
  • buffMass Assault: Minimum Training Level reduction increased from -5% to -10%.
  • changeMass Assault: Minimum Training Level -5% replaced with +2% Reinforce Rate.

⚙️Tank Modules(14)

  • buffRocket Launcher: Breakthrough increased from -2 to 4, Hard Attack increased to 4, and added 4 Defense.
  • buffImproved Rocket Launcher: Breakthrough increased from -2 to 8, Hard Attack increased to 6, and added 8 Defense.
  • nerfAnti-Air 2: Air Attack reduced from 32 to 30.
  • nerfAnti-Air 3: Air Attack reduced from 46 to 42.
  • nerfEasy Maintenance: IC cost reduction reduced from -7.5% to -5%.
  • buffEasy Maintenance: XP cost reduced from 30 to 20.
  • nerfEasy Maintenance: Reliability bonus reduced to 7.5%.
  • buffCast Armor: Now provides +10% HP.
  • buffSloped Armor: Now provides +5% HP.
  • buffWelded Armor: Now provides +5% HP.
  • buffAuto-Loader: Now provides +2% Soft Attack and +2% Air Attack.
  • buffStabilizer: Now provides +4% Hard Attack.
  • buffSmoke Launchers: Breakthrough increased from 1 to 2.
  • buffExtra Ammunition Storage: Defense increased to 5 and Breakthrough increased to 3.

🔫Land Units(6)

  • buffBicycle Infantry: Support Equipment requirements reduced from 10 to 5.
  • buffMotorized Infantry: HP increased to 27.5.
  • nerfMechanized Infantry: Soft Attack bonus of +10% removed.
  • nerfAmphibious Mechanized Infantry: Soft Attack bonus of +10% removed.
  • buffCavalry: Now has a +20% Breakthrough bonus.
  • buffSupport Units: HP increased to 1.6 for Artillery, Motorized Artillery, Rocket, Motorized Rocket, Truck-Drawn Rocket, Anti-Tank, Anti-Air, Motorized Anti-Tank, and Motorized Anti-Air.

🧪Technologies(2)

  • buffImproved Infantry Equipment I & II: Soft Attack bonus to Motorized & Mechanized Infantry increased from +5% to +10%.
  • nerfProximity Fuzes: Naval AA bonus reduced to +15%.

🐞Bug Fixes(5)

  • fixAmphibious Tanks: Reverted the fix that prevented superstructures from allowing larger guns on Amphibious Tanks due to technical issues.
  • fixTrade Interdiction: Submarine Attack +0.1 replaced with Torpedo Attack +10%.
  • fixMarine Commando: Pioneers now correctly provide +15% Armor bonus to Amphibious Armor.
  • fixConvoy Escort: Fixed a bug in efficiency computation for convoy escort/raiding when an admiral covers 33+ regions.
  • fixMultiplayer: Fixed an Out-of-Sync error occurring when very large numbers were used in mods.

💻Performance & Modding(2)

  • fixCore Engine: Improved computational precision for exponents, logarithms, and power functions.
  • nerfStrategic Destruction: Interception Mission Efficiency bonus lowered to +15%.

Summary

Experimental Tank Mechanics

This Open Beta update introduces two major experimental features for armored warfare. First, tank chassis now provide multiplicative bonuses to module stats based on their technological tier, incentivizing the research of Modern and Advanced chassis over Interwar models. Second, a new reliability-scaling mechanic has been added, where equipment HP now scales directly with its reliability stat (0-100%), rewarding players for high-quality designs.

Doctrine and Unit Rebalancing

Land doctrines have seen a significant shift, particularly targeting the dominance of 'Large Unit Tactics' by restricting its supply bonuses to Leg Infantry. Conversely, 'Mobile Infantry' and 'Mobile Warfare' have received buffs to Soft Attack and Breakthrough to improve the competitiveness of motorized and mechanized divisions. Additionally, base HP has been increased for a wide range of support units including Artillery, Anti-Tank, and Anti-Air pieces.

← OlderHOI IV | Open Beta SE™ Update 2Aug 12, 2026

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