Dev Diary | HOI IV-X Anniversary Update

Generals!

The Decade

A decade. It still feels strange to write. Hearts of Iron IV turns Ten this month, and somehow the most unbelievable number in our telemetry isn't the millions of techs researched or wars declared, it's this one: 39% of the people who started playing HoI4 back in 2016 are still playing today. Ten years on. Another is that HoI IV has been going on longer than WW2 actually took: 2194 days for WW2, 3652 (and counting) for HOI IV.

The game has changed enormously since launch: most mechanics have deeper experiences, focus trees are very different and much more exhaustive, the AI plays the game better, and we are able to keep closer to the historical timeline than ever before. But the core vision, as described 12 years ago, still holds true. One thing we did not necessarily foresee, even if it was a core part of the vision at the start, was the adaptation of mods to the degree we see today. We’ve also seen two Game Directors transition to new internal projects, and we will talk about who will take over on June 18th!

“Our hope for this game is that you as a player will feel in control of a real global conflict and want to learn the tools of warfare in an open sandbox environment during this intense period of history. Our goal with Hearts of Iron IV is to create a WWII game completely focused on Global Strategic Warfare.” - Dan Lind, 2014

The Patch

This anniversary's War Effort patch leans heavily into Naval AI, picking up the threads 1.17.4 left hanging. We extended the open beta longer than usual, specifically so you could help us. This anniversary patch also brings a wealth of late game performance improvements, fixing some of the worst offenders, and a rebalancing of the naval gameplay we trialed earlier in the year. With the release of Thunder at Our Gates next week, another large free update will be released as well!

We have some cool stuff planned:

• 11th of June - Thunder at Our Gates release 🥳

• 18th of June - Anniversary “behind the scenes” video + teaser of what is coming up next.

I also wanted to give a shout out to both our multiplayer and youtube community. Our youtube channel has grown over the years, and is one of the biggest ones we have compared to our other Paradox titles! It’s a, perhaps unusual, source of additional insight into our players minds. Then not to speak about all the great content creators making great videos about HoI IV.

HoI 4 multiplayer is really fun to play, we play it every week at the office, but it's also really fun to watch crazy 60+ people multiplayer games. And I just wanted to mention that we are aware of some of the problems we have with lobbies/hacking, and we are working on this at the moment.

We'll keep the post-release support going up until our Swedish-mandated Summer holiday, and pick straight back up as needed once we're back.

To every player who has shaped this game over the last ten years, and to every developer past and present who has poured themselves into it: Thank you. Here's to the next decade.

/Niels Uiterwijk - Studio Manager

What have you all been up to these years:

Where players have been sending their boats these last years

Interestingly (maybe?) we have a short animated version, but the variance is so low that it basically looks exactly like the static image above.

PATCH NOTES

(1.18.3.0.7709 (d7cc))

Ship & Navy Balance

• Reduced Naval Minimum Chance to Hit from 2% to 0.5%

• Set Naval XP Gain for the following mission types: Patrol, Convoy Raiding, Convoy Escort, Mines Planting, Mines Sweeping to 0.2, and Strike force to 0.05

• Navy Mastery gain for Strike force missions increased from 0 to 0.05, and for Convoy Raiding increased from 0.2 to 0.3

• Supply Consumption of Carriers reduced from 1.2 to 0.8

• Supply Consumption of Battleships reduced from 0.8 to 0.56

• Supply Consumption of Battlecruisers reduced from 0.48 to 0.32

• Supply Consumption of Heavy Cruisers reduced from 0.4 to 0.24

• Naval Reform Spirit changed from +15% Naval Experience Gain to +10% Naval Mastery Gain

• Naval Sub-Doctrine Coastal Mine-laying Clearing Procedures reward no longer applies bonus to mine sweeping to the Submarines, instead the effect on Destroyers has been increased from +20% to +25%

• Long Range Submarines Sub-Doctrine Ocean Patrols reward now also applies +10% bonus to the surface detection to the Nuclear Submarines

• Long Range Submarines Sub-Doctrine Improved Dive Protocols reward now also reduces Surface Visibility of the Nuclear Submarines by 5%

• Long Range Submarines Sub-Doctrine Support the Surface reward now also applies +10% bonus to the Torpedo Attack, and Naval Speed to the Nuclear Submarines

• Removed Resource Cost from most of the naval modules (guns, deck armor, hangar decks), Armor Schemes as well as Anechoic Tiles will still have resource costs associated with them.

• Cruiser Armor Scheme Resource Costs changed from resource cost of 0/1/1/2 Steel to 0/0/1/1 Steel and from 0/0/1/1 Chromium to 0/0/0/1 Chromium

• Battleship Armor Scheme Resource Costs changed from resource cost 1/1/2 Steel to 1/1/1 Steel. Chromium Costs unchanged.

• Early Destroyer Naval Range increased from 1500 km to 2000 km

• Basic Destroyer Naval Range increased from 1800 km to 2500 km and service manpower reduced from 325 to 300

• Improved Destroyer Naval Range increased from 2000 km to 3000 km and service manpower reduced from 400 to 350

• Advanced Destroyer Naval Range increased from 2500 km to 3500 km and service manpower reduced from 500 to 400

• Advanced Destroyer Hull cost decreased from 4 Steel to 3 Steel

• Naval Dominance Factor for Advanced Destroyers increased from 40 to 42

• Light Ship Engine III - Fuel Consumption lowered from 10 to 9

• Early Cruiser Hull cost increased from 1 Steel to 2 Steel

• Improved Cruiser Hull cost increased from 2 Steel to 3 Steel

• Advanced Cruiser Hull cost increased from 3 Steel, to 3 Steel and 1 Chromium

• Improved Cruiser Naval Range reduced from 4000 km to 3500 km and service manpower reduced from 1200 to 1000

• Advanced Cruiser Naval Range reduced from 4500 km to 4000 km and service manpower reduced from 1400 to 1200

• Cruiser Ship Engine I - Production Cost reduced from +15% to +12.5% and increased Naval Speed from +20% to +25%

• Cruiser Ship Engine II - Production Cost reduced from +17.5% to +15%

• Cruiser Ship Engine III - Production Cost reduced from +20% to +17.5%

• Cruiser Ship Engine IV - Production Cost reduced from +22.5% to +20%

• Pre-Dreadnaught Hull Naval Range increased from 2250 km to 2500 km

• Pre-Drednought Ship Hull cost changed from 1 Steel 1 Chromium to 2 Steel

• Torpedo Cruiser Naval Range reduced from 4000 km to 3500 km and service manpower reduced from 960 to 900

• Panzerschiff service manpower reduced from 1800 to 1200, IC cost for the hull reduced from 3500 to 2800, surface visibility from 22 to 18.

• Panzerschiff Hull cost increased from 3 Steel to 3 Steel 1 Chromium

• Coastal Defense Ship service manpower reduced from 1800 to 1000. IC cost for the hull reduced from 3500 to 1500. Base Steel Cost reduced from 3 to 2. Surface Visibility reduced from 20 to 16. Naval Range increased from 1500 km to 2000 km.

• Coastal Defense Ship Hull cost decreased from 3 Steel to 2 Steel

• Coastal Defense Ship Max Strength (HP) increased from 100 to 110

• Basic Heavy Hull service manpower reduced from 5200 to 4300

• Improved Heavy Hull service manpower reduced from 6000 to 4650

• Advanced Heavy Hull service manpower reduced from 6000 to 5000

• Modern Heavy Hull service manpower reduced from 6000 to 5000, IC cost for the hull reduced from 4000 to 3600

• Early Heavy Ship Hull cost increased from 1 Steel 1 Chromium to 3 Steel 1 Chromium

• Basic Heavy Ship Hull cost increased from 1 Steel 1 Chromium to 3 Steel 1 Chromium

• Improved Heavy Ship Hull cost increased from 1 Steel 1 Chromium to 4 Steel 1 Chromium

• Advanced Heavy Ship Hull cost increased from 1 Steel 1 Chromium to 4 Steel 1 Chromium

• Modern Heavy Ship Hull cost changed from 6 Steel 3 Chromium 2 Tungsten to 5 Steel 2 Chromium 2 Tungsten

• Early, Basic, Improved, Advanced Heavy Ship Hull Fuel Consumption reduced from 67 to 60

• Early Heavy Ship Naval Dominance Factor increased from 300 to 325

• Modern Heavy Ship Hull Fuel Consumption reduced from 80 to 72

• Heavy Ship Engine I - Production Cost reduced from +17.5% to +12.5%, increased Naval Speed from +20% to +25% and increased Fuel Consumption from 20 to 22

• Heavy Ship Engine II - Production Cost reduced from +20% to +15% and increased Fuel Consumption from 25 to 28

• Heavy Ship Engine III - Production Cost reduced from +22.5% to +17.5% and increased Fuel Consumption from 30 to 34

• Heavy Ship Engine IV - Production Cost reduced from +25% to +20% and increased Fuel Consumption from 35 to 40

• Super Heavy Hull service manpower reduced from 9000 to 7000

• Super Heavy Ship Hull cost increased from 1 Steel 1 Chromium to 5 Steel 2 Chromium

• Super Heavy Ship Hull Fuel Consumption reduced from 75 to 68

• Basic Carrier Naval Range increased from 3000 km to 3500 km and service manpower reduced from 4500 to 4000

• Improved Carrier Naval Range increased from 4000 km to 4250 km and service manpower reduced from 5000 to 4500

• Advanced Carrier service manpower reduced from 5500 to 5000

• Modern Carrier service manpower reduced from 6500 to 6000

• Basic Carrier Ship Hull cost increased from 3 Steel 1 Chromium to 4 Steel 1 Chromium

• Improved Carrier Ship Hull cost increased from 4 Steel 1 Chromium to 5 Steel 2 Chromium

• Advanced Carrier Ship Hull cost increased from 4 Steel 2 Chromium to 6 Steel 2 Chromium

• Modern Carrier Ship Hull cost increased from 5 Steel 3 Chromium to 6 Steel 3 Chromium

• Converted Battleship, Basic, Improved and Advanced Carrier Ship Hull Fuel Consumption reduced from 87 to 70

• Modern Carrier Ship Hull Fuel Consumption reduced from 90 to 72

• Improved Carrier Ship Hull Naval Dominance Factor increased from 300 to 325

• All Carriers Surface Detection Reduced from 26 to 20 and Sub Detection from 5 to 1

• Deck Space Carrier Detection Values increased from +5 Carrier Surface Detection and +2 Carrier Sub Detection to +8 Carrier Surface Detection and +4 Carrier Sub Detection

• Carrier Ship Engine I - Naval Speed reduced from +30% to +25% and increased Fuel Consumption from 12 to 16

• Carrier Ship Engine II - Naval Speed reduced from +40% to +35% and increased Fuel Consumption from 16 to 24

• Carrier Ship Engine III - Naval Speed reduced from +50% to +45% and increased Fuel Consumption from 20 to 32

• Carrier Ship Engine IV - Naval Speed reduced from +60% to +55% and increased Fuel Consumption from 24 to 40

• Cruiser Carrier Conversion Naval Range reduced from 4000 km to 3000 km

• Battleship Carrier Conversion Naval Range reduced from 4000 km to 3000 km and service manpower from 5000 to 3500

• Converted Cruiser Ship Hull Fuel Consumption reduced from 87 to 60

• Escort Carrier IC cost for the hull reduced from 1500 to 1250 and service manpower reduced from 2500 to 1500

• Escort Carrier Ship Hull cost changed from 2 Steel 1 Chromium to 3 Steel

• Escort Carrier Deck Space Carrier Detection Values increased from +2 Carrier Surface Detection & +5 Carrier Sub Detection to +5 Carrier Surface Detection and +7 Carrier Sub Detection

• Escort Carrier Ship Hull Fuel Consumption reduced from 87 to 50

• Ice Carrier Ship Hull cost increased from 5 Steel 2 Chromium to 8 Steel 2 Chromium

• Ice Carrier Ship Hull Fuel Consumption reduced from 95 to 90

• Ice Carrier Deck Space Carrier Detection Values increased from +6 Carrier Surface Detection and +3 Carrier Sub Detection to +10 Carrier Surface Detection and +4 Carrier Sub Detection

• Reduced SUBMARINE_HIDE_TIMEOUT from 20 to 8 and SUBMARINE_REVEALED_TIMEOUT from 16 to 12. This means that revealed submarine in battle will hide after 8 hours, and if the submarine taskforce was attacked they will stay revealed for 12 hours at the start of the combat.

• Penalty from Positioning to the Submarine Visibility reduced from +200% to +100%

• Reduced Shallow Waters effect on Submarine Visibility from +100% to +33%

• SUBMARINE_REVEAL_DETECTION_MULTIPLIER reduced from 0.075 to 0.065

• Early Submarine Sub Visibility reduced from 25 to 22 and Strength increased from 10 to 15

• Basic Submarine Sub Visibility reduced from 22 to 20 and Strength increased from 20 to 22.5

• Improved Submarine Sub Visibility reduced from 20 to 18

• Advanced Submarine Strength increased from 35 to 37.5

• Submarine Carrier Hull cost increased from 3 Steel to 4 Steel

• Submarine Ship Engine II - Now reduces the Submarine Visibility by -3.5%

• Submarine Ship Engine III - Submarine Visibility Reduction increased from -5% to -7% and reduced Fuel Consumption from 10 to 9

• Submarine Ship Engine IV - Production Cost reduced from +20% to +17.5%

• Submarine Nuclear Engine - Now reduces the Submarine Visibility by -15% and increased Naval Speed from +10% to +20%

• AdjustedNaval retreat rebalancedBASE_ESCAPE_SPEED increased from 0.045 to 0.05, SPEED_TO_ESCAPE_SPEED reduced from 0.95 to 0.5, ESCAPE_SPEED_PER_COMBAT_DAY increased from 0.01 to 0.015, MAX_ESCAPE_SPEED_FROM_COMBAT_DURATION increased from 0.15 to 0.5, ESCAPE_SPEED_SUB_BASE increased from 0.08 to 0.1, ESCAPE_SPEED_HIDDEN_SUB increased from 0.18 to 0.35, and capital ships and carriers now retreat at half their usual strength threshold (CAPITAL_SHIP_COMBAT_RETREAT_MULT added at 0.5).

• Convoy production deficit boost is now capped to avoid starving warship production

• NAVAL_STRIKE_CARRIER_MULTIPLIER increased from 10.0 to 12.0

• CARRIER_COMBAT_DAMAGE_STATS_MULTIPLIER increased from 0.35 to 0.5

Other Balance

• Heavy MG Fighter armament costs more IC (2x +20%, 4x +30%) and 4x mounts (light & heavy) take -2.5% reliability

• AdjustedNationalist ChinaReduced focus time from 70 days to 35 days for 21 focuses across the Industry, Army, Air, Navy, and Politics branches

• Nationalist China: Construct the Banqiao Dam moved earlier in the tree; The National Sun Yat-sen University takes its previous prerequisites

Gameplay

• A new, very challenging achievement: "Steiner!": As Germany, after June 22nd 1941, reach more than 30% surrender progress while at war with the Soviet Union, France, and England. Afterwards, control Moscow, Paris, and London.

• Carrier Sortie Settings now only apply to the first 24 hours of Naval Combat, instead of being tracked for 24h per Carrier - even when they were reinforcing an already ongoing battle

• Screening bonus now scales with screening efficiency: partially screened formations no longer receive the full screening bonus against capital fire

• Strike forces are now able to target combats that are already in combat, while they exit their own combat

• Strike forces with a valid strike target will now ignore active combats on the way (no more being distracted by pesky subs!)

• Quality of Life: Buying equipment on international market now selects the maximum by default, and auto sets the minimum acceptable civ count

• Made lendlease default to max amount for 'once' and to 100% for 'percentage' modes

• Lendlease has better UI logic and will default to maximum amounts that the receiver can handle with their convoys

• Updated supply tooltip to show more careful where all supply is coming from

• An event will now be fired to all the signatories of the Nine-powers treaty when China gets attacked

Stability & Performance

• Use static_cast instead of dynamic_cast in CConstRef release builds. The debug path already validates the cast via assertion, making the RTTI overhead in release unnecessary. Improves performance for all ref pointer dereferences.

• optimized navalhq calculations

• Added a sound pool system, which keeps sound effects in memory for up to ~20 seconds, which should reduce file system access and thus reduce stutters

• Micro optimizations to supply system

• _NavalNodesByBaseSupply is now just a flat array rather than a weird 2d array

• Removed linear search for dirty tracking, instead do a direct lookup

• Added caching to root & fallback orders, significantly speeding up unit code

• Improved performance when having a large army selected

• Batched ability refresh on reinforcements arrival. (Now happens atmost once instead of twice)

• Trade is now calculated per resource, as most calculations are done per resource, which saves performance

• Naval objectives don't get recalculated all the time anymore, instead they are recalculated every X days

• Added a pre-pass for ai theatre distribution, cutting down massively on the number of options looked at

• Fixed leaking of sound effects, causing a slow down in longer game sessions.

• Equipment variants processing speed up significantly

• Calculating fuel requested for airplanes is 90% faster

• Airwings accident chance has a pre-roll now, skipping tens of thousands of calculations late game

• Fixed memory leak that caused late game performance problems for AI

• Parallelized airbase status updates

• Equipment data will be compacted once per year, reducing late game performance problems

• Fixed performance in very large scale naval battles (1000+ ships)

• Reduced math operations from doing a full 4x4 update to just do a vector2f and a single scale float

• Added a landmass detection, stopping world wide pathfinds

UI

• Tooltip updated to indicate that control ratio required for having dominance in a sea zone is 60% instead of 66%

• Added Hit Profile 'Stat' to be displayed on Ship Designer as well on the Ship Cards. Minelaying/Minesweeping will be displayed only if their respective value is above 0.

• Added ability to filter divisions based on their type in the division overview window

• Repair-now button will stop the current mission so the fleet can focus on repair

AI

• AI naval ship templates for Italy, England, USA, Japan, and the generic fallback reworked: most ship classes now follow a four-tier scheme (early / basic / improved / advanced) tied to historical classes as close as possible. AI fleets are now better-equipped at each tier and progress through them more reliably.

• AI is able to swap better quality ships into current task forces

• AI is better at picking a homebase that can reach all regions

• Added logic for the AI to decide that it is losing the battle too hard, and go for a full retreat instead of a slow retreat

• Introduction of AI buffering ships, this should result in the AI keeping a reserve fleet on hand for reinforcements

• Large lendleases will no longer be accepted if they would take too many convoys to ship

• Ai will be more aggressive with advantageous naval invasions

• Navy AI now considered scripted fleets separately for the case of building its required & optional task forces

• When naval objectives overlap, they will consider that and reduce request for patrols due to that

• Coastal defense will prioritize assignment based on number of VP's being defended

• Germany will build more submarines and fewer surface ships, matching historical doctrine

• Multiple invasions into the same sea region will share a single defense objective

• Naval dominance strategies with negative values will properly suppress objectives

• Coast defense will only ramp up when enemy presence is detected

• Rebalanced AI weights for naval research

• Introduced CV Fighter / Naval bomber equipment progress for England

• The AI will now train their troops more often

• The AI will no longer train divisions that are next to the enemy

• The AI will try to train their fleets a bit more opportunistic

• The AI will be a bit more sensible with picking a homebase for its standby fleet

• If there are no more patrol fleets available, the AI will use Strike forces as patrols instead

• Added logic to prevent the AI from assigning too many patrols to support naval invasion

• AI now reserves more dockyards for repair (thank you forum feedback)

• The AI will now repair until critical damage has been repaired (thank you forum feedback)

• The AI will now use their escort fleets in regions, even if the region is blocked due to convoy raiding

• Italy commits fewer units to the Alexandria push and holds Africa longer. Slightly reduced England's Alexandria defense buffer.

• UK builds up North Africa port more if its needed to push to Tobruk

• Convoy danger now decays quicker with time

• AI signatories of the Nine-Power Treaty now always agree to abandon it when Chiang Kai-shek leads China (unless allied with Japan)

Modding

• Introduced naval_invasion_support_priority to direct the naval AI more

• AI objectives will respect blocked naval regions now and not consider them for naval mission assignment anymore

• Fixed a bug where the AI was not using fleets if the ships did not require any fuel

• Equipment role debug view shows raw matching score

Bugfix

• Fixed a rare crash that happened due to order invalidating

• Fixed a bug where taskforces could be in two naval combats at the same time

• Fixed a bug where ships were partially considered for supply need

• Fixed a bug where a strike force sometimes gets stuck on an invalid target and stops working

• Fixed a bug where wrong snow modifier values were shown + fixed a bug where the leader snow adjuster didn't work as intended

• Snow attack penalty is now shown on the move-arrow tooltip

• Removed legacy plane techs from BBA-enabled starts for 36 minor nations

• RI Bolzano in the 1939 OOB now uses the correct ship_hull_cruiser_2 (Bolzano Class)

• Convoy raiders won't join or reinforce a combat unless there are enemy convoy's to shoot at

• Fixed a crash related to carrier airplanes being deployed

• Fixed bug where emergency convoy demand would scale infinitely

• Fixed a bug where a ship would gain strength through doctrines, on reloading a save they would be damaged

• Fixed a bug where planes destroyed by other sources than air to air combat did not count to war participation (as an example: static anti-air or destroyed planes in a raid)

• AddedRajFixed "Mixed Economy" giving resources on all owned states rather than starting states and added coal.
• FixedRajFixed "The riches of the Raj" to check for synthetic referinies as well
• AddedRajFixed "Acquire new Resources" so it gives the resources to the correct state

• CTD that could occur with scientists in late game

• Fixed a bug where a naval supply tooltip would show a much larger number of convoys required then was actually needed

• Fixed OOS related to trade routes

And lastly we’d like to let you know that we have a special Hearts of Iron IV Ten Year Anniversary Store and it’s live now! Steam post image