Ten years. It still feels surreal to write that. This month, Hearts of Iron IV officially celebrates its tenth anniversary. Looking at our telemetry, the most staggering statistic isn’t the millions of technologies researched or the countless wars declared—it’s this: 39% of the players who first picked up HoI4 back in 2016 are still active today. Even more remarkable is the timeline itself. World War II lasted 2,194 days; HoI IV has been operational for over 3,652 days and counting.
The game has evolved profoundly since launch. Mechanics have gained nuance, focus trees have become vastly more expansive and detailed, the AI is more competent than ever, and we have tightened our adherence to historical accuracy. Yet, the core vision outlined 12 years ago remains our guiding light. While we didn’t fully anticipate the sheer scale of the modding community’s contributions, it has become an integral part of the experience. We have also seen two Game Directors move on to new internal projects, and we look forward to introducing their successors on June 18th.
“Our hope is that you, the player, feel in control of a global conflict, mastering the tools of warfare within an open sandbox throughout this pivotal era. Our objective for Hearts of Iron IV is to deliver the definitive WWII experience focused on Global Strategic Warfare.” – Dan Lind, 2014
The War Effort patch marks this milestone by significantly refining Naval AI, building upon the foundations laid in 1.17.4. We extended our open beta period specifically to gather your feedback, which has been instrumental. This release also delivers substantial late-game performance optimizations and a comprehensive rebalancing of naval gameplay. With the launch of Thunder at Our Gates next week, another major free update will also go live.
Here is what we have in store:
- June 11th: Thunder at Our Gates release. 🥳
- June 18th: Anniversary “Behind the Scenes” video + a teaser for what lies ahead.
I would also like to extend my gratitude to our multiplayer and YouTube communities. Our YouTube presence has expanded impressively, becoming a vital window into the minds of our players—not to mention the incredible work of our content creators. While our weekly office multiplayer sessions are a highlight, we are well aware of the current frustrations regarding lobbies and security, and our team is actively addressing these issues.
We will maintain consistent post-release support until our summer break, resuming work immediately upon our return. To every player who has helped shape this journey over the last decade, and to every developer—past and present—who poured their passion into this game: Thank you. Here is to the decade ahead.
/Niels Uiterwijk – Studio Manager
Where players have been deploying their fleets:
While we created a short animation for this data, the consistency of player behavior is so high that it is virtually identical to the static image above.
(1.18.3.0.7709 (d7cc))
- Reduced Naval Minimum Chance to Hit from 2% to 0.5%.
- Standardized Naval XP gain for various missions: Patrol, Convoy Raiding, Convoy Escort, Mine Planting, and Mine Sweeping set to 0.2; Strike Force set to 0.05.
- Increased Navy Mastery gain: Strike Force to 0.05; Convoy Raiding increased from 0.2 to 0.3.
- Lowered Supply Consumption: Carriers (1.2 to 0.8), Battleships (0.8 to 0.56), Battlecruisers (0.48 to 0.32), and Heavy Cruisers (0.4 to 0.24).
- Naval Reform Spirit updated: now provides +10% Naval Mastery Gain instead of +15% Naval Experience.
- Rebalanced submarine doctrines and Destroyer mine-sweeping bonuses (+20% to +25%).
- Nuclear Submarines receive improved surface detection, lower surface visibility, and better torpedo attack via new doctrine rewards.
- Removed resource costs for most naval modules; Armor Schemes and Anechoic Tiles remain resource-dependent.
- Revised resource requirements for Cruiser and Battleship armor schemes.
- Increased Naval Range and reduced service manpower requirements across all Destroyer tiers; decreased Steel cost for Advanced Destroyer Hulls.
- Adjusted production costs and performance metrics for Cruiser engines and hulls.
- Reduced IC costs and manpower for Panzerschiff and Coastal Defense ships.
- Rebalanced Heavy Ship hull costs, fuel consumption, and manpower requirements.
- Reduced Carrier manpower and updated Deck Space detection values.
- Refined submarine visibility, timeout logic, and positioning penalties.
- Adjusted Naval retreat thresholds and escape speeds.
- Increased NAVAL_STRIKE_CARRIER_MULTIPLIER to 12.0 and CARRIER_COMBAT_DAMAGE_STATS_MULTIPLIER to 0.5.
- Increased IC costs for Heavy MG Fighter armaments and adjusted reliability penalties.
- Nationalist China: Reduced focus times from 70 to 35 days for 21 historical focuses; streamlined construction of the Banqiao Dam.
- New Achievement: “Steiner!”: As Germany, reach 30% surrender progress while at war with the USSR, France, and UK after June 22nd, 1941, then seize Moscow, Paris, and London.
- Improved screening logic: partially screened formations no longer receive full screening bonuses.
- Refined Strike Force targeting to prevent distraction by submarines and active secondary combats.
- UI/QoL: Added auto-select for international market purchasing and lend-lease defaults.
- Events: Notifications added for Nine-Power Treaty signatories upon an attack on China.
- Optimized reference pointer dereferences using static_cast.
- Enhanced NavalHQ, supply system, and airbase status update calculations.
- Implemented a sound pool system to reduce file system stuttering and fixed memory leaks.
- Significant late-game performance improvements through year-based equipment compaction and air-wing logic optimizations.
- Fixed memory leaks during prolonged sessions and optimized large-scale naval battle performance.
- Reworked AI ship templates for major nations; AI now employs a tiered (early/basic/improved/advanced) progression system.
- Improved AI strategic logic: better home-base selection, reserve fleet management, and aggressive naval invasion planning.
- Refined AI response to convoy raiding and coastal defense, including prioritization of victory points.
- Optimized resource management: the AI now reserves dockyards for repairs and utilizes escort fleets more effectively.
- General AI improvements for Nationalist China, Italy, and the UK.
- Resolved rare crashes related to order invalidation and carrier aircraft deployment.
- Fixed bugs involving task forces in simultaneous naval combats and incorrect naval supply tooltip readouts.
- Corrected OOS issues related to trade routes.
- Resolved several historical OOB and focus-related errors for Raj and other minor nations.