Nuclear Weapons

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Nuclear Mushroom

Nuclear weapons have been available in HOI2 since the game was first released. In the Doomsday expansion, Nukes became very noticeable in the "Doomsday Scenario" which begins with a US nuclear strike on the Soviet Union. Being nuked is the worst thing that can happen to your nation. The only thing worse than being nuked, however, is being nuked twice. It will completely disrupt everything you do, and severely challenge your ability to wage war. Any sustained series of five or more nuclear strikes will render your nation completely helpless.


Nuclear research contains 8 industrial technologies, and five secret weapon technologies. After researching the "Isotope Separation Facility" technology, it is possible to begin building nuclear reactors. In order to produce nuclear weapons, you need one province containing at least six reactor levels. To help you with that, reactors can be built in only one province: so be sure to place your first reactor in the proper place. Each successive technology allows building one additional reactor level. More advanced reactors provide research bonuses. The "Nuclear Waste Bomb" secret technology enables a reactor size of 6, which is the minimum reactor size necessary for the production of nuclear weapons. This technology also enables the strategic bombardment mission "nuke". Reaching this stage requires an investment of 54,000 IC-days in reactor building.

Once your reactor has reached level six, nuclear bombs will be produced automatically. Hover the mouse cursor over the "Atom" symbol in the middle of the top status bar to get a tooltip about when your next nuke will be ready.


Nukes can initially be delivered via strategic bombers. After research of the "Miniaturized Fission Bomb" (1948), in conjunction with all rocketry Industrial technologies, and all four rocketry secret weapons, it is possible to attach nukes to rockets. In order to attach a nuke to any of those delivery devices, select the latter and click the "attach nuke" button at the bottom of the unit's info screen. It's very similar to attaching regular brigades.

Once there is a nuke attached, the whole formation (e.g. the strategic bomber group) has a new mission available: "nuke".


The damage caused by a nuclear weapon varies based on the technology level researched. The first, "Nuclear Waste Bomb" technology is the default level, while the "Semi-Fission Bomb" increases damage by 30%, the Fission bomb by an additional 50%, and the Hydrogen bomb another 50%.

Nuclear weapons act as a kind of permanent strategic bombardment, multiplied by several orders of magnitude. Several well-placed nukes can severely hamper the infrastructure of any nation and make the target nation incapable of fighting war. They have several serious effects to the province that was struck:


In the original HOI2 game, nuclear weapons had one effect: complete destruction of all units in the province nuked.

Starting in HOI2 DD, nuclear weapons reduce the strength of all existing units, and wipe out organization. In addition, since the nuked province has 0% infrastructure, the soldiers are effectively trapped in that province, and will not regain organization. Therefore, strategic redeployment is necessary to properly "recover" the use of the effected units.


A successful nuclear strike against a province will permanently reduce IC, infrastructure, and manpower in province. It will "temporarily" reduce AA, land forts, airbases, ports, and resources.

For example, in the Doomsday scenario, before the nuke, Moscow has: 27 IC, 4 AA, 5 Fort; 13 MP, 31 Metal, 82 energy, 17 rare, 5 airbase, 70% infrastructure. After the nuke, 0 of 9.6 IC, 0.8 of 4 AA, 0/5 Fort, 4 MP, 1.57 Airbase, 0.1% infrastructure. Meanwhile resources are all temporarily reduced: metal was reduced by 83%, energy by 78%, and rares by 83%.

The "temporary" reductions are a bit misleading. With 0.1% infrastructure, these will take years to come back at full strength. While the player can rebuild infrastructure in the affected province, each level of infrastructure takes 1 year to build. Thus, in all practical warfare terms, even the "temporary" damage is essentially permanent.


A successful nuclear strike against your nation will increase national dissent. Based on the Doomsday scenario (Fission Bomb technology), the following results were produced:

Target Dissent Caused Victory Points Original IC Original Manpower
Moscow 23.85% 50 27 13
Leningrad 10.8% 30 18 3
Stalingrad 8.1% 30 16 1
Kiev 2.7% 5 2 2
Kuybyshev 2.7% 0 2 2
Moyz 0% 0 0 0

This means that dissent caused is a function of IC and manpower: Victory points are not involved. In order to determine dissent lost, the equation is:

D = (I * 0.45) + (M * 0.9)

Where D = Dissent; I = IC; and M = manpower. Thus, manpower has twice the weight of IC in determining dissent caused.

Technology Formula
Nuclear Waste Bomb D = (I * 0.25) + (M * 0.5)
Semi-Fission Bomb D = (I * 0.30) + (M * 0.7)
Fission Bomb D = (I * 0.45) + (M * 0.9)
Hydrogen Bomb

Huge dissent, together with the other effects of nuclear weapons, spells disaster during wartime. For example, in the Doomsday scenario, after the nuclear strike, the Soviet Union's transport capacity skyrockets to almost 40% over the limit, while total effective industrial capacity drops by an incredible 30%. The problems in transport capacity have a ripple effect throughout the military, with unit combat effectiveness dropping by 20%. Meanwhile, the IC reduction makes it nearly impossible to lower the massive dissent while maintaining production, supplies, and reinforcements. Since the prospects of lowering dissent are unrealistic, in practical terms, the 30% IC loss is permanent.

Calling the effects of a nuclear strike devastating are an understatement. Again, the only thing worse than one nuclear strike is a second nuclear strike.

Top Targets

The most strategically important target for a nuclear weapon are the nuclear reactors of your adversaries. Since the game only allows building a single reactor of varying levels (at tremendous cost), the first nuclear power that can launch a weapon against the opponent's reactor ensures nuclear supremacy. A reactor hit by a nuclear weapon will be "temporarily" reduced to 0. Due to the 0% infrastructure in the province hit, however, it would take years for that reactor to fully recover. Moreover, expanding that reactor will be extremely delayed. In this sense -- nations with nuclear ambitions that have not yet reached the critical threshold can be permanently prevented from attaining nukes with recurring strikes once every few years.

The following image shows the top ten nuclear targets that would cause the most dissent, based on data from the 1936 scenario. Note that this does not account for any new IC built during the course of the game. Due to the weight of manpower in determining dissent, Nationalist China is the most susceptible to the adverse effects of dissent caused by nuclear warfare. Nationalist China predictably has 4 of the top 10 targets, and in the event of a successive strike, Nationalist China would suffer 72.5% dissent from just 4 targets. No other major or minor nation would exceed 40% dissent after 4 nuclear strikes, making it exceedingly difficult to cause 100% dissent (thus triggering civil war) through nuclear strikes.


Nuclear Research technologies confer different damage ratings for nuclear devices. The following table was made from in-game testing with a target of Berlin (20 IC, 10 MP, 100% Infrastructure). Note that damage from nuclear devices is not consistent, and there are variances in damage rates (around 25% margin of error). Since a nuclear weapon both temporarily and permanently reduces IC and infrastructure, these values have been listed separately:

Technology Level Temporary IC Permanent IC Temporary Infra Permanent Infra Manpower remaining
Nuclear Waste Bomb 5 13 45% 70% 5
Semi-Fission Bomb 2 10 20% 55% 5
Fission Bomb 0 6 0.1% 33% 1
Hydrogen Bomb 0 0 0.1% 0.23% 0

Defense against nuclear strikes

Nukes that are delivered by Strategic Bombers can be defended against with air superiority:

  • Constant flights of interceptors/fighters in a perimeter around your nation
  • Strong air defense installations in a perimeter around your nation, or you most valuable core provinces
  • Strong infrastructure of radar and airbases to improve interceptor/fighter efficiency
  • Focus on enemy airbases within range of your nation

Nukes based on rockets such as the ICBM cannot be defended against.

Game shortfalls

HOI2 modeling of nuclear weapons is not perfect, and it is one of several notable AI flaws. In particular, the AI reacts so poorly to the use of nuclear weapons that many consider their use gamey:

  • Non-use: The AI usually will not research/build nuclear weapons. This is particularly ahistorical. The AI will only use them in the Doomsday scenario, because they are already researched/built.
  • Surrender: The AI will not surrender, no matter how many times it is nuked. This defect includes the Japanese AI. The use of nuclear weapons is not a factor in peace negotiations.
  • Deterrence: The AI does not fear complete nuclear devastation nor does it have any deterrence mechanism, resulting in highly irrational decisions (e.g. if the player is capable of launching a massive nuclear strike against the AI, the AI will still launch a single nuke that does little damage to the player, while retaliation from the player completely destroys the AI).

The following potential failings are debatable, but often mentioned in discussions:

  • Diplomatic consequences: The game does not model negative diplomatic consequences of sustained nuclear warfare (relations with all nations dropping, raising belligerence, and even dissent at home, etc)
  • Fallout: There is no nuclear fallout. This is historically reasonable with early nukes, whose most devastating effects were mostly thermal and radiation exposure was limited.
  • Nuclear Winter: The game does not model the cumulative effects of massive nuclear warfare on the environment (e.g. resource drops around the world).

Finally, one error/bug in the game design is that nuclear reactors do not produce energy: this was incorrectly stated in the game manual, and is incorrectly stated in the "Nuclear Power Production" technology.


Build Time

Reactor Size Build Time
6 400 days
7 320 days
8 270 days
9 160 days

Technology Teams

Only a limited number of countries have a technology team capable of researching nuclear technology:

  • Austria
  • Canada (past 1943)
  • Communist China (past 1950)
  • Nationalist China (past 1950)
  • Denmark
  • France
  • Germany
  • Holland
  • Hungary
  • Ireland
  • Italy
  • Japan
  • Luxembourg
  • Poland
  • Switzerland
  • Soviet Union
  • Nationalist Spain
  • Republican Spain
  • Sweden
  • United Kingdom
  • United States

The following nations are special, break-away nations that can only exist in special circumstances, but who will have nuclear technology teams:

  • California
  • Congo
  • Confederate States of America (past 1943)
  • East Germany (past 1954)
  • West Germany
  • India (past 1943)
  • Russia (RUS)
  • Scandinavia
  • Slovenia
  • Transural Republic (past 1942)
  • Wallonia

Version Changes

In HOI2 DD, nuclear weapons underwent a complete change: there role was modified to have several strategic consequences, listed below. In the original HOI2 game, nuclear weapons only destroyed all units in a province. In DD version 1.1, minor changes were that the AI began targeting nuclear reactors for installation strike missions, where previously they had been ignored. In DD version 1.3, nuclear reactors cost an additional 5 manpower.

Use of Nukes in Mods

The AI in the following mods will develop and use nuclear weapons:

  • TRP
  • Compendium
  • Confederate Armageddon

In DAIM, the AI will research and build nuclear weapons. The AI will "not", however, launch nuclear weapons. Typically this is because the AI will not build rockets or strategic aircraft which are necessary to deliver the weapons.

Enable Nukes manually

Following advice from Gen.Schuermann, you can edit the game files of the vanilla game or any mod to enable nukes:

  1. Open up the specific savegame you want to mod.
  2. Look for the country to edit, by searching country = {
  3. Scroll down, to the part of construction.
  4. Look at max_factor = x. Standard is max_factor = 0.020 (this means, afaik, that Ger will use 2% of their total available IC for construction of either IC, AA, Airports, ports, rocket facilities, infra, and finally, nukes. Say, Germany has 300 effective IC. a nuke facility costs 50 IC.
  5. Change max_factor = 0.200 (ensure to lower all other infrastructure priorities)
  6. Then look for nuclear_reactor = no. Switch no to yes.
  7. Next, look for technology. Technology = { is the search entry.
  8. There should be a spot "ignore techs". Identify the nuke tech numbers in order to ensure the AI will research them.
  • Industrial Tech IDs: 5470 5480 5490 5500 5510 5520 5530 5540
  • Secret Tech IDs: 7170 7180 7190 16010 16020