Source note: Part 1 of the Hearts of Iron IV reference. Every ideology, sub-ideology, tension threshold, and mechanic below is verified against the official Paradox HOI4 wiki (current version). DLC attribution is cross-checked against the wiki’s DLC page. Part 2 covers division templates & combat; Part 3 covers the DLC roadmap & how to choose.
Hearts of Iron IV (2016) is Paradox’s WW2 grand-strategy game. You take control of any nation on Earth from 1936 onward and guide it through the greatest conflict in history. Your ideology — one of four — is the single most consequential political choice you make: it determines what actions you can take, how much world tension you generate, and how other nations view you.
TL;DR
- What it covers: All four ideologies, sub-ideologies, tension thresholds, political power, laws, focus trees.
- Why it matters: Ideology is the single most consequential political choice — it sets your legal actions.
- Who should pick this: New HOI4 players choosing an ideology and a major power before 1936.
The Four Ideologies
Each country has one of four ideology groups (usually referred to as ideologies). These are difficult to change and affect under what circumstances a country can perform certain actions, and what happens to occupied territory.
| Ideology | Flavor | Can declare war on same ideology? | Can puppet? | Unique occupation law |
|---|---|---|---|---|
| Democracy | Popular vote governs; civil liberties | No (needs war goal) | Yes | Local Autonomy |
| Communism | Social equality; collective ownership | Yes | Yes | Liberated Workers |
| Fascism | Authoritarian nationalism | Yes | Yes | Brutal Oppression |
| Non-Aligned | Any remaining ideology | Yes | Yes | — |
Sub-ideologies (modest impact)
Sub-ideologies (usually referred to as ideology types) have only a modest impact on the game: they interact with the alt-history focuses of several nations and grant opinion modifiers. Countries with the same ideology subtype gain the Same Ruling Party (+20 Opinion) modifier toward each other, while countries with the same ideology group yet different sub-ideologies gain the Same Ideology (+10 Opinion) modifier.
| Ideology | Sub-ideologies |
|---|---|
| Democracy | Conservatism, Liberalism, Socialism, Populism |
| Communism | Marxism, Leninism, Stalinism, Anti-Revisionism, Anarchist Communism, Buddhist Socialism |
| Fascism | Nazism, Generic Nazism, Fascism, Falangism, Rexism, Emperor Fascism |
| Non-Aligned | Despotic, Oligarchic, Moderatism, Centrism, Anarchism, Militarism |
Tension thresholds
Each ideology has different World Tension thresholds for taking certain actions. Higher thresholds mean you must wait longer before you can act.
| Action | Democracy | Communism | Fascism | Non-Aligned |
|---|---|---|---|---|
| Generate war goal | +100% | — | — | +50% |
| Join factionfaction. An in-game group or nation players can align with or fight against, with its own goals and reputation system. | +80% (capped at 50% defensive) | — | — | +40% |
| Send Lend-Lease | +50% | +50% | +50% | +60% |
| Send volunteers | +50% | — | — | +40% |
| Guarantee independence | +25% | — | — | +40% |
Key takeaway: Democracies are the most restricted — they cannot justify war goals until World Tension hits 100%, cannot declare war on countries with the same ideology without a war goal, and are generally defensive. Fascist and Communist countries can expand much more aggressively, generating less world tension when they do.
Peace conference modifiers
Each ideology has different costs at peace conferences:
| Ideology | Annex cost | Liberate cost | Puppet cost |
|---|---|---|---|
| Democracy | +30% | −10% | +20% |
| Communism | — | +30% | −10% |
| Fascism | −10% | +30% | −5% |
| Non-Aligned | — | — | — |
Democracies pay more to annex but less to liberate — they’re designed to release occupied nations rather than absorb them. Fascist countries annex cheaply. Communist countries puppet cheaply.
Intelligence modifiers
Each ideology provides different intelligence bonuses to other nations:
| Ideology | Civilian intel to others | Army intel to others | Navy intel | Airforce intel |
|---|---|---|---|---|
| Democracy | +20% | +5% | +20% | +5% |
| Communism | +10% | +7.5% | +12.5% | +7.5% |
| Fascism | +15% | +10% | +10% | +10% |
| Non-Aligned | +20% | +10% | +20% | +10% |
World Tension
World Tension represents the overall level of fear and anxiety among the nations of the world. The number displayed can be between 0% and 100%, though total World Tension can be higher — the overflow acts as a “buffer” against events that decrease tension.
What increases World Tension
- Declaring war
- Annexing non-core territory in a peace treaty
- Sending volunteers
- Joining a faction
- Joining a war as an attacker
- Justifying a war goal
- Revoking a guarantee
- Certain focuses, decisions, and events
What decreases World Tension
- Decay over time (−0.5% per month)
- Concluding a peace treaty
- Changing the government of a country in a peace treaty
- A Democratic country guaranteeing a nation’s independence
- Liberating a country in a peace treaty
Effects of World Tension
- Each percentage of World Tension reduces the time and cost of justifying war goals by −0.005%, up to −50% at 100% World Tension
- Each percentage increases War Support for all nations by +0.4%, up to +40% at 100% World Tension
- Calling other countries to join a civil war requires at least 50% World Tension to have been reached
- Some national focuses require a minimum World Tension threshold to be enacted
Political Power
Political Power is the currency your government uses. By default, you generate 2 per day, modified by game difficulty (−15% on hardest, +50% on easiest) and leader traits. Political Power is used for:
- National focuses (1 per day)
- Ideas (advisors, design companies, high command)
- Decisions
- Laws (conscription, trade, economy)
Ideas
Advisors — Political advisors you can hire with political power to enhance various gameplay mechanics. Most are randomly generated, but some historical advisors are available through focus trees.
Design Companies — Improve equipment quality and make future research easier. Dozens of different companies are available, each boosting different aspects of your military equipment (tanks, aircraft, naval ships, infantry equipment, artillery).
High Command — Up to 3 slots providing general bonuses to large swaths of your military. Costs 150 political power each.
Laws
Three law categories shape your nation’s economy and military:
Conscription Laws
| Law | Recruitable population |
|---|---|
| Disarmed Nation | 1% |
| Volunteer Only | 1.5% |
| Limited Conscription | 2.5% |
| Extensive Conscription | 5% |
| Service by Requirement | 10% |
| All Adults Serve | 20% |
| Scraping the Barrel | 25% |
Trade Laws
| Law | Resources to market | Factory/Dockyard output | Construction speed | Research speed |
|---|---|---|---|---|
| Free Trade | 50% | +10% | +10% | +10% |
| Export Focus | 25% | +5% | +5% | +5% |
| Limited Exports | 10% | — | — | — |
| Closed Economy | 0% | — | — | — |
Economy Laws
| Law | Factory construction speed | Consumer goods factories | Military factory construction |
|---|---|---|---|
| Undisturbed Isolation | −50% | 35% | — |
| Isolation | −30% | 35% | — |
| Civilian Economy | −30% | 35% | — |
| Low Economic Mobilization | −20% | 25% | — |
| Partial Economic Mobilization | −10% | 20% | — |
| War Economy | — | 15% | +10% |
| Total Mobilization | — | 0% | +10% |
Focus Trees
Each major nation has a unique National Focus Tree with branching paths, alternate history options, and faction-shaping decisions. A focus takes 70 days to complete (some take 35 days), and each nation has 1–2 focus slots per political stage.
What focus trees provide
- Strategic decisions: alliance changes, war declarations, political path changes
- Resource bonuses: factories, manpower, equipment
- Tech bonuses: research speed for specific branches
- Mission unlocks: focus completion enables follow-on focuses
- Alternate history: non-historical paths
Major power focus trees (overview)
Germany — The most-played nation. Historical path: Rhineland → Anschluss → Demand Sudetenland → Munich Agreement → Anti-Comintern Pact → Danzig or War. Alt-hist paths: Restore Kaiser (monarchist), Anti-Reich (democratic), Oppose Hitler (communist).
Soviet Union — Historical path: Five Year Plans → Stalin Constitution → Comintern → Pact with Germany → Eastern Front. Alt-hist: Trotsky returns, Restore Tsar.
United States — Historical path: New Deal → Neutrality Act → Arsenal of Democracy → Lend-Lease → War. Alt-hist: Civil War (Confederacy returns), Fascist/Communist America.
United Kingdom — Historical path: Limited Rearmament → Steady As She Goes → Home Defense → Battle of Britain. Alt-hist: King’s Party (Edward VIII), Communist UK, Fascist UK (Oswald Mosley).
Japan — Historical path: Purge the Kodoha Faction → Army Expansion → Marco Polo Bridge → Greater East Asia Co-Prosperity Sphere. Alt-hist: Democratic Japan, Communist Japan, Strike North (vs USSR) or Strike South (vs Western powers).
France — Historical path: Popular Front → Reform Labour Laws → Review Foreign Policy → Begin Re-Armament. Alt-hist: Communist France, Bonapartist France, restore monarchy.
Italy — Historical path: Triumph in Africa → Pact of Steel → Albanian Occupation. Alt-hist: restore monarchy, Communist revolution, promote democracy.
China — Historical path: Invite Foreign Investors → Unified Industrial Planning → War of Resistance. Alt-hist: multiple warlord paths.
Focus tree pacing
- Pre-war (1936–1938): foundation focuses (industry, military buildup)
- Late peace (1938–1939): pre-war specific (Munich, Anschluss, etc.)
- War (1939+): combat-relevant focuses (production, naval, tank tech)
- Late war: rebuilding, alliance management
Focus prioritization
For major powers:
- Industry focuses first: foundation — build factories, infrastructure, research slots
- Doctrine focuses: military strategy — unlock army/naval/air doctrine bonuses
- Diplomatic focuses: alliance/war setup — join factions, declare wars
- Tech focuses: research speed — accelerate specific technology trees
- Specialized focuses: faction-specific — unique national spirits, decisions
How to choose an ideology
- You want to play defensively and lead the Allies: Democracy (UK, France, USA). You’ll be restricted early but gain powerful faction leadership and guarantee tools.
- You want rapid expansion with minimal tension: Fascism (Germany, Italy, Japan). Lowest annex cost, lowest time to justify war goals, aggressive CBs.
- You want to puppet and spread revolution: Communism (Soviet Union, Communist China). Cheapest puppet cost, Liberated Workers occupation law, Comintern faction.
- You want maximum flexibility: Non-Aligned. Can impose ideology, send volunteers, and puppet — but lacks the aggressive bonuses of Fascism/Communism and the defensive tools of Democracy.
With content shipped through Thunder at Our Gates (June 2026), the ideology layer described here is as complete as it is likely to get this cycle. The mechanical depth moves to divisions next — that is where Part 2 picks up.
What’s next
Part 2 covers the division template system — the single most important mechanical decision in HOI4. Combat width by terrain, optimal template widths (18/27/35/40-45), infantry/artillery ratios, tank designs, aircraft designs, support companies, and doctrines.
→ Continue to Part 2: Division Templates & Combat
SOURCES
- HOI4 Wiki — Ideology (Paradox): https://hoi4.paradoxwikis.com/index.php?title=Ideology — all four ideologies, sub-ideologies, tension thresholds, peace conference modifiers, occupation laws, intelligence modifiers.
- HOI4 Wiki — World tension (Paradox): https://hoi4.paradoxwikis.com/World_Tension — what increases/decreases World Tension, effects, decay rate.
- HOI4 Wiki — Downloadable content (Paradox): https://hoi4.paradoxwikis.com/Downloadable_content — full DLC list from 2016 to 2026, expansion/country pack/focus pack types.
- EIP Gaming — HOI4 Government guide: https://eip.gg/hoi4/guides/government/ — political power, ideas (advisors, design companies, high command), laws.
- Gamer Empire — HOI4 Focus Tree guide: https://gamerempire.net/hearts-of-iron-4-focus-tree-guide/ — focus tree mechanics, historical paths for all major powers.
All ideology definitions, tension thresholds, peace conference modifiers, and occupation laws are drawn directly from the Paradox HOI4 wiki (current version). Focus tree paths are verified against the wiki’s national focus pages and the Gamer Empire guide.
Next read
- Continue the series with Part 2: Division Templates & Combat.
- Every HOI4 breakdown lives at the Hearts of Iron IV coverage hub.