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Hearts of Iron IV
Hearts of Iron IV
Apr 2, 2026
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HOI IV - Open Beta Update II

4/5 Significant

Submarines receive massive survivability buffs through detection formula reworks, while Carriers see base detection nerfed in favor of deck module specialization.

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Key Changes

  • 1Submarine passive reveal chance reduced by 25% and hide timeout slashed from 20 to 8 hours.
  • 2Resource costs removed from most naval modules including guns, deck armor, and hangar decks.
  • 3Carrier base detection significantly nerfed, shifting detection power to Deck Space Modules.
  • 4Shallow Waters visibility penalty for submarines reduced from +100% to +33%.
  • 5Manpower requirements reduced for almost all ship hulls, including a 2000-man reduction for Super Heavy Hulls.
  • 6Supply consumption for Carriers, Battleships, and Cruisers reduced by approximately 30-40%.
  • 7Operational range increased for all Destroyer tiers to improve escort capabilities.
  • 8Sea zone dominance requirement reduced from 66% to 60%.
  • 9Naval XP gain rates significantly increased for Strike Force and Patrol missions.
  • 10Coastal Defense Ship and Panzerschiff hulls received major IC cost and visibility buffs.

All Changes

⚓Naval Gameplay(10)

  • buffSubmarines: Reduced SUBMARINE_REVEAL_DETECTION_MULTIPLIER from 0.1 to 0.075, reducing passive reveal chance by ~25%.
  • nerfSubmarines: Increased SUBMARINE_REVEAL_TORPEDO_FIRING_DETECTION_MULTIPLIER from 1 to 1.1, increasing reveal chance when firing by 10%.
  • buffSubmarines: Reduced SUBMARINE_HIDE_TIMEOUT from 20 to 8 hours, shortening the time subs stay visible after reveal.
  • buffSubmarines: Reduced SUBMARINE_REVEALED_TIMEOUT from 16 to 12 hours for defending submarines.
  • buffSubmarines: Reduced SUBMARINE_REVEAL_ON_MINIMUM_POSITIONING from 2 to 1, lowering visibility penalty at 0% positioning from +200% to +100%.
  • buffSubmarines: Reduced Shallow Waters visibility penalty for submarines from +100% to +33%.
  • changeNaval Combat: Reduced minimum naval hit chance from 2% to 0.5%.
  • changeNaval Reform Spirit: Naval Reform Spirit changed from +15% Naval Experience Gain to +10% Naval Mastery Gain.
  • buffNaval Missions: Increased Naval XP gain for Patrol, Convoy Raiding, Convoy Escort, and Mine missions to 0.2.
  • buffStrike Force: Increased Naval XP gain for Strike Force missions to 0.5.

🚢Ship Hulls(31)

  • buffEarly Submarine Hull: Early Submarine Hull visibility reduced from 25 to 22 and strength increased from 10 to 15.
  • buffBasic Submarine Hull: Basic Submarine Hull visibility reduced from 22 to 20 and strength increased from 20 to 22.5.
  • buffImproved Submarine Hull: Improved Submarine Hull visibility reduced from 20 to 18.
  • buffAdvanced Submarine Hull: Advanced Submarine Hull strength increased from 35 to 37.5.
  • nerfCarriers: All Carrier hulls base Surface Detection reduced from 26 to 20 and Sub Detection from 5 to 1.
  • buffCarriers: Carrier supply consumption reduced from 1.2 to 0.8.
  • buffBattleships: Battleship supply consumption reduced from 0.8 to 0.56.
  • buffBattlecruisers: Battlecruiser supply consumption reduced from 0.48 to 0.32.
  • buffHeavy Cruisers: Heavy Cruiser supply consumption reduced from 0.4 to 0.24.
  • buffEarly Destroyer: Early Destroyer range increased from 1500km to 2000km.
  • buffBasic Destroyer: Basic Destroyer range increased to 2500km and manpower reduced to 300.
  • buffImproved Destroyer: Improved Destroyer range increased to 3000km and manpower reduced to 350.
  • buffAdvanced Destroyer: Advanced Destroyer range increased to 3500km and manpower reduced to 400.
  • changeImproved Cruiser: Improved Cruiser range reduced to 4000km but manpower reduced to 1000.
  • buffAdvanced Cruiser: Advanced Cruiser manpower reduced from 1400 to 1200.
  • changeTorpedo Cruiser: Torpedo Cruiser range reduced to 3500km and manpower reduced to 900.
  • buffPanzerschiff: Panzerschiff manpower reduced to 1200, IC cost reduced to 2800, and visibility reduced to 18.
  • buffCoastal Defense Ship: Coastal Defense Ship range increased to 2000km, manpower reduced to 1000, and IC cost reduced to 1500.
  • buffPre-Dreadnaught Hull: Pre-Dreadnaught Hull range increased from 2250km to 2500km.
  • buffBasic Heavy Hull: Basic Heavy Hull manpower reduced from 5200 to 4300.
  • buffImproved Heavy Hull: Improved Heavy Hull manpower reduced from 6000 to 4650.
  • buffAdvanced Heavy Hull: Advanced Heavy Hull manpower reduced from 6000 to 5000.
  • buffModern Heavy Hull: Modern Heavy Hull manpower reduced to 5000 and IC cost reduced to 3600.
  • nerfCruiser Carrier Conversion: Cruiser Carrier Conversion range reduced from 4000km to 3000km.
  • changeBattleship Carrier Conversion: Battleship Carrier Conversion range reduced to 3000km and manpower reduced to 3500.
  • buffBasic Carrier: Basic Carrier range increased to 3500km and manpower reduced to 4000.
  • buffImproved Carrier: Improved Carrier range increased to 4250km and manpower reduced to 4500.
  • buffAdvanced Carrier: Advanced Carrier manpower reduced from 5500 to 5000.
  • buffModern Carrier: Modern Carrier manpower reduced from 6500 to 6000.
  • buffEscort Carrier: Escort Carrier IC cost reduced to 1250 and manpower reduced to 1500.
  • buffSuper Heavy Hull: Super Heavy Hull manpower reduced from 9000 to 7000.

⚙️Naval Modules(4)

  • buffCarrier Deck Space Module: Carrier Deck Space Module Surface Detection increased to 8 and Sub Detection to 4.
  • buffIce Carrier Deck Space Module: Ice Carrier Deck Space Module Surface Detection increased to 10 and Sub Detection to 4.
  • buffEscort Carrier Deck Space Module: Escort Carrier Deck Space Module Surface Detection increased to 5 and Sub Detection to 7.
  • buffNaval Modules: Removed resource costs from most naval modules including guns, deck armor, and hangar decks.

💎Economy & Resources(24)

  • buffCruiser Armor Scheme: Cruiser Armor Scheme Steel and Chromium costs reduced across multiple tiers.
  • buffBattleship Armor Scheme: Battleship Armor Scheme Steel cost reduced from 2 to 1 for the final tier.
  • nerfSubmarine Carrier Hull: Submarine Carrier Hull Steel cost increased from 3 to 4.
  • buffAdvanced Destroyer Hull: Advanced Destroyer Hull Steel cost reduced from 4 to 3.
  • nerfEarly Cruiser Hull: Early Cruiser Hull Steel cost increased from 1 to 2.
  • buffBasic Cruiser Hull: Basic Cruiser Hull Steel cost reduced from 3 to 2.
  • buffImproved Cruiser Hull: Improved Cruiser Hull Chromium cost removed.
  • buffAdvanced Cruiser Hull: Advanced Cruiser Hull Steel cost reduced from 4 to 3.
  • nerfTorpedo Cruiser Hull: Torpedo Cruiser Hull Steel cost increased from 2 to 3.
  • nerfPanzerschiff Hull: Panzerschiff Hull Steel cost increased to 3 and added 1 Chromium cost.
  • buffCoastal Defense Ship Hull: Coastal Defense Ship Hull Steel cost reduced from 3 to 2.
  • changePre-Dreadnought Ship Hull: Pre-Dreadnought Ship Hull Steel cost increased to 2 and Chromium cost removed.
  • nerfEarly Heavy Ship Hull: Early Heavy Ship Hull Steel cost increased from 1 to 3.
  • buffBasic Heavy Ship Hull: Basic Heavy Ship Hull Steel cost reduced from 4 to 3.
  • nerfImproved Heavy Ship Hull: Improved Heavy Ship Hull Steel cost increased from 1 to 4.
  • buffAdvanced Heavy Ship Hull: Advanced Heavy Ship Hull Steel cost reduced from 5 to 4.
  • buffModern Heavy Ship Hull: Modern Heavy Ship Hull Steel cost reduced to 5 and Chromium cost reduced to 2.
  • buffSuper Heavy Ship Hull: Super Heavy Ship Hull Chromium cost reduced from 3 to 2.
  • buffBasic Carrier Ship Hull: Basic Carrier Ship Hull Steel cost reduced from 5 to 4.
  • buffImproved Carrier Ship Hull: Improved Carrier Ship Hull Steel cost reduced from 6 to 5.
  • buffAdvanced Carrier Ship Hull: Advanced Carrier Ship Hull Steel cost reduced from 7 to 6.
  • buffModern Carrier Ship Hull: Modern Carrier Ship Hull Steel cost reduced from 8 to 6.
  • buffIce Carrier Ship Hull: Ice Carrier Ship Hull Steel cost reduced from 10 to 8.
  • changeEscort Carrier Ship Hull: Escort Carrier Ship Hull Steel cost increased to 3 and Chromium cost removed.

🖥️UI/UX(1)

  • changeSea Zone Tooltip: Updated sea zone dominance tooltip to reflect the new 60% control ratio requirement (down from 66%).

Summary

Naval Detection Rework

This update focuses heavily on the naval meta, specifically targeting submarine survivability. The detection formula has been overhauled to reduce passive reveal chances and shorten the time submarines remain visible after being spotted. Shallow waters and low positioning penalties have been significantly toned down to prevent early-game submarines from being instantly destroyed.

Carrier and Ship Balancing

Carriers have had their 'free' base detection stats reduced, shifting that power into Deck Space Modules. This forces players to specialize their carriers rather than receiving high detection stats by default. Additionally, a sweeping balance pass has reduced manpower requirements and supply consumption for most heavy ship classes while extending the operational range of destroyers.

Economic Overhaul

Resource costs have been removed from most naval modules, including guns and hangar decks. Ship hull costs and resource requirements (Steel and Chromium) have been adjusted across the board, generally making larger hulls more accessible in terms of manpower and production cost.

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