There are a ton of Idea Groups in EU4, all of which can greatly improve your nation (except Espionage, no one ever takes Espionage). 

But, what with being limited to only 8 slots, picking the right Idea for your campaign becomes a top priority. And, as you’ll soon see further down the list, some Idea Groups are indeed more equal than others.

 

10) Offensive

Offensive, like the name suggests, is a great Idea Group if you’re planning on waging plenty of wars. From better generals to better quality and faster sieges, there are few Ideas with the same amount of wide-reaching bonuses that can drastically affect the war you’re fighting.

Specifically talking about the generals, usually, the only thing that affects how many pips, or points, a general can have is Army Tradition. Which is, coincidentally, one of the few modifiers this Idea Group doesn’t actually have. 

That being said, having the ability to guarantee 2 pips is very good, both in the early-game, when Army tradition is low, and late-game, when you have a higher chance of getting the more valuable Siege pips instead of Fire and Shock ones.

Of course, generals aren’t the only thing that benefits from this Idea. The extra 20% Siege ability will shorten sieges considerably, and in fact, if you could manage to stack enough Siege ability modifiers, each siege tick would take only a few days! And those numbers simply aren’t possible without Offensive.

Of course, the strategic influences of this Idea Group also impact your strategic reserves. Having larger armies, not to mention more of them, allows you to properly project your power across the world and wage long, devastating wars. Something that you simply wouldn’t be able to do without the extra force limit granted by this Idea. 

Of course, the extra discipline the Idea provides helps keep losses low as well, which is very useful in any prolonged engagement.

Finally, each Idea Group has a certain policy that you can select that gives you extra bonuses, depending on the combo. And while there certainly are good bonuses to be had with Offensive, I believe that your policy slots are better used on other, more useful combinations.

In summary, the most important things this idea gives you are:

-Better generals

-Larger armies

-Faster sieges

Idea group bonuses and notable policies:

• +1 Land leader shock
• −10% Recruitment time
• +1 Land leader fire
• +100% Prestige from land battles
• +20% Siege ability
• +20% Land force limit modifier
• +5% Discipline

      Finisher: +5% Recover army morale speed
      Good policy combo: Offensive+Innovative +10% Siege ability, +1 Land leader siege

 

9) Exploration

Exploration is the Idea you take if you want to play as a colonizer. Be it as a nation in Western Europe, East Asia, or even Africa, Exploration gives you all the tools necessary for you to establish yourself throughout the world.

Giving you explorers and conquistadors which you can use to beat back the previously impenetrable Terra Incognita of the world’s oceans, as well as previously uncharted lands.

From giving you the opportunity to colonize said uncharted lands via dedicated colonists and even increasing the total distance you can send your people to unknown lands. And even making it free to expel any undesirables to grow your colonies quicker, the fact of the matter is that no true conquest of the New World can be done without this group.

Add to that the fact that it also allows you to increase your naval dominance by fielding a  much larger fleet. As well as giving you the ability to claim any overseas native land, if you’re not a fan of naturally colonizing the land yourself.

Overall, the Idea is very focused on what it does, and it’s certainly a must-have pick for anyone trying out the colonial game. Though it should be said, while the bonuses are very nice, they don’t really do much more than what they say. Sure, colonial nations are great and all, but they take a ton of time to actually achieve that greatness. 

As a result, it’s usually recommended to only really take this Idea Group if you have allies to help defend you, or you’re not in any position to be threatened. 

As for the policies, again, they are mainly focused on naval and colonial buffs. Though in certain cases, most notably with any nation that has an increase to vassal force limit in their national ideas such as Andalusia, it can be very powerful to pair this idea with aristocratic.

In summary, the most important things this idea gives you are:

-The ability to explore and colonize the New World

-More efficient diplomats

-A larger navy

Idea group bonuses and notable policies:

Allows recruitment of explorers & conquistadors

• +1 Colonist
• +50% Colonial range
• +10 Global settler increase
• +10% Global tariffs, −20% Envoy travel time
• −100% Expel minorities cost
• +25% Naval force limit modifier

      Finisher: Can fabricate claim overseas in colonial regions
      Good policy combo: Exploration+Aristocratic +33% Maximum Manpower

 

8) Religious

It is obvious that with religion playing such a big role in the game, you have to address it at some point. And one of the two picks that you have for dealing with religion is the aptly named, Religious Ideas.

The bonuses are fairly straightforward. It gives you more missionaries, better missionaries, and even cheaper missionaries. And not only that, but it also makes your True Faith provinces much more stable, as well as increasing any modifiers of the religion of your choice. 

Beyond that, Religious also helps keep your country stable with a reduction to the cost to increase your stability, as well as making it cheaper to convert any problematic peoples in your empire.

And best of all? It gives you a free casus belli on all wrong religion countries that border you, be they heathens or heretics. Now I know what you’re thinking, why would this be the best part of the Idea Group, since surely the ability to convert any wrong religion provinces would be better? 

Well, it all comes down to the core gameplay loop of the game.

You see, the best parts of the game are, bar none, war, and conquest. And in the early game, unless you happen to start with some of your cores being owned by another nation, or heavens forbid, losing a war, the only way to get a CB is to fabricate a claim. Now, that in-and-of-itself isn’t a problem. The problem, is how long it takes. 

Fabricating a claim can take upwards of a few years, and when most of the fun you can get is fighting armies and sieging provinces, waiting doesn’t sound very appealing. In comes Religious with the perfect CB. You only have to have a different religion than your neighbors to get it. 

So the most use out of this Idea will get either those countries that start surrounded by heathens and heretics, or those who belong to a smallor unique religion to begin with, such as Byzantium or any of the Japanese or Mesoamerican nations

Overall, this is an incredibly good Idea to pick if you’re planning on expanding a lot, especially if you have to also convert the land you conquer. Though, speaking of policies, it does feel slightly lackluster. It does give some good bonuses, but those bonuses also tend to be fairly small in nature, ie. either +5% or +10% ones which, while OK, aren’t the best thing in the world.

In summary, the most important things this idea gives you are:

-Solving your religious problems by making everyone follow the True Faith

-Very cheap stability and culture conversions

-A really good CB in the early game

Idea group bonuses and notable policies:

• +1 Missionary
• -25% Stability cost modifier
• +3% Missiany strength
• +2 Tolerance of the True Faith, +2 Yearly papal influence / +0.5 Yearly devotion / +0.25 Monthly fervor / +0.1 Monthly piety / +10% Church power / +0.5% Yearly patriarch authority / +10% Yearly karma decay / +1 Yearly doom reduction /+0.15 Yearly authority
• +1 Yearly prestige
• −50% Missionary maintenance cost
• Permanent casus belli against neighboring heathens and heretics

      Finisher: −25% Culture conversion cost, +10% Brahmins loyalty equilibrium / +10% Clergy loyalty equilibrium
      Good policy combo: Religious+Trade +10 Goods produced, +1 Missionary strength

 

7) Trade

If ever there was an Idea Group designed to make you money, it was this one. Just like how interconnected our real world is, you are now able to experience the power of the free market exchange for yourself firsthand with Trade Ideas.

Giving you a frankly obscene amount of Merchants with which you can assert your dominance in any trade node within your trade range. Trade range, that, coincidentally, is also increased with this Idea Group. 

Furthermore, it also directly increases how much income you gain from collecting trade, as well as increasing how much trade you steer towards your main trade nodes. Something that, while it doesn’t seem that powerful at first glance, might actually be the most powerful way to increase your income. Provided it’s all connected correctly, that is.

You see, for each merchant that steers trade towards another node, he adds an additional 5% trade value to it. And the best part about this added value? It stacks. 

So if you manage to connect several nodes with merchants, all sending their trade to wherever you may be collecting it, you end up with a massive bonus towards the end. Which means that if you’ve ever wanted to earn buckets of ducats, then this Idea Group is the best one for the job. 

Of course, Trade also has the single most powerful economic policy in the game. Namely, the 20% Goods produced modifier, which will be expanded upon later, as well as many other combos that further increase your income.

In summary, the most important things this idea gives you are:

-Many more merchants which drastically increase your income

-Trade-related bonuses that further boost your income

Idea group bonuses and notable policies:

• +20% Global trade power
• +1 Merchant
• +25% Trade range
• +10% Trade efficiency
• +1 Merchant
• +25% Trade steering
• +25% Caravan power

      Finisher: +1 Merchant
      Good policy combo: Trade+Quantity +20% Goods Produced

 

6) Quality

There is one reason why you’d pick Quality, and one reason alone. To make Space Marines.

Jokes aside, if you’re looking to purely beef up your troops, then Quality is here to make that task easier. From increasing the combat ability of all of your units to giving a flat boost to everyone in the form of extra discipline. To even increasing your army tradition, giving you a variety of bonuses which can further help your nation fight wars.

It even helps the often forgotten navy. True, the naval aspect of the game is fairly slim, as the majority of gameplay is related to land and land combat. But naval bonuses, however useless they may be, are still nice to have. 

Especially when trying to invade problematic island nations, like Great Britain or Japan, which can be a very annoying hustle if you can’t either scare their ships away, or beat them in a straight fight.

Despite being so high on the list, there really isn’t much to say about this Idea. The things it does, it does excellently and it is an undeniable boon to whoever takes this Idea. Speaking of which, it doesn’t matter who picks this. 

You can be a major nation, drowning in military bonuses, like Prussia, or a mercantile trade empire, like the Dutch, and you’ll still get benefits from picking this Idea Group.

Of course, the policies themselves are also very much focused on buffing your military, and the buffs you can get are all for the most part very good and useful.

In summary, the most important things this idea gives you are:

-Highest quality armies

-Not terrible ships

Idea group bonuses and notable policies:

• +10% Infantry combat ability
• +0.5 Yearly army tradition
• +10% Cavalry combat ability
• +5% Ship durability
• +10% Morale of navies
• −25% Naval attrition
• +10% Artillery combat ability

      Finisher: +5% Discipline
      Good policy combo: Quality+Eco 5% Discipline

 

5) Humanist

Humanist is the second option you can choose when it comes to dealing with religious issues, and unlike Religious, every nation can benefit from Humanist.

OK, hear me out on this. Religious is great because you can conquer provinces and quickly convert them. It’s also great because you get a fantastic CB for the early game. 

That being said, while only a few nations, like Byzantium, can become ridiculously stable with Religious, with Humanist, every country can achieve the same sort of stability.

From having less separatism to more tolerance and religious unity. From more promoted cultures and less national unrest to better relations with countries and even cheaper ideas. If you’ve ever had struggles with the stability of your nation, Humanist was basically designed to solve all of your issues.

Now, religious and unrest ideas aside, the idea cost reduction that the Idea Group finishes with is actually incredibly good. Very few things lower the price of ideas, and unlike tech, the price of which actually lowers the more ideas you take, the price of ideas is always the same. So having some way to actually save a few monarch points on them is actually really powerful.

That being said, personally, the most powerful bonus out of any in this Idea Group would probably be the improve relations modifier. Sure, you can use it as intended and improve your relations, which is a useful thing to actually do. However, improve relations modifiers actually have a secret effect that the game doesn’t actually tell you about. 

Rather, they increase AE decay, essentially making it so that you can conquer land more frequently, at less of a threat from coalitions! That being said, it’s also pretty funny that the improve relations modifier from humanist is actually higher than the improve relations modifier from Diplomatic.

Policy-wise, Humanist actually has incredibly solid picks, none of which are bad.

In summary, the most important things this idea gives you are:

-Solving your religious problems by making friends

-Less separatism, which means fewer revolts

-Faster AE decay

Idea group bonuses and notable policies:

• +25% Religious unity
• -2 National unrest, +25% Religious harmonization speed
• +2 Tolerance of heretics
• -10 Years of separatism
• +2 Max promoted cultures
• +30% Improve relations
• +Tolerance of heathens

      Finisher: -10% Idea cost / +0.25 Yearly harmony increase / +10% Brahmins loyalty equilibrium / +10% Dhimmi loyalty equilibrium
      Good policy combo: Humanist+Diplo +1 Max promoted cultures, +20% Improve relations

 

4) Diplomatic

Honestly, the spot could’ve either gone to Diplomatic or Influence, since both do similar things, and are useful in surprisingly similar manners. In the end though, while Influence is a very good Idea Group, Diplomatic has more general uses and is the more player-nation oriented Idea of the two.

What do I mean by that? Well, both nations give you extra diplomats, as well as extra diplomatic relations and diplomatic reputation. However, where Influence is more useful for a vassal swarm type of playstyle, or, really, any playstyle that involves playing with vassals, Diplomatic shines better on its own.

Aside from the aforementioned bonuses, you also get more improve relations from this Idea. As well as, and this is probably the most powerful bonus of the Group, cheaper province warscore cost.

The 20% reduction is no joke, and it allows you to annex countries that you otherwise wouldn’t have been able to. In fact, this is such a massive advantage, that for anyone doing a world conquest, this Idea is a near mandatory pick.

As a result, for an Idea Group that can be used throughout the game, Diplomatic firmly deserves the spot it received. As for the policies it has access to, many of them are of meh quality, though, the ones that give you more leaders or diplomats are always a solid pick.

In summary, the most important things this idea gives you are:

-More and better diplomats

-Cheaper provinces in peace deals

-Easier alliances and quicker AE decay

Idea group bonuses and notable policies:

• +1 Diplomat
• +1 Diplomatic relation
• +1 Diplomat
• +25% Improve relations
• +2 Diplomatic reputation
• −20% Province warscore cost
• −10% Diplomatic technology cost

      Finisher: Lowered impact on stability from diplomatic actions
      Good policy combo: Diplo+Quality +1 Diplomatic reputation, -0.05 Monthly war exhaustion

 

3) Economic

I have to confess something. I personally am not a fan of Economic Ideas, and rarely, if ever use them myself and I even debated putting them here. That being said, I simply cannot deny the absolutely mind-boggling potential this Idea Group has.

From boosting your income through various means, such as straight increases to your tax and production. As well as cheaper building construction costs and troops. And even reducing inflation and giving you more favorable loans. 

To helping you centralize your provinces faster so you can reap their full benefits sooner. This Idea Group is certainly going to help you make money, much like its name suggests.

That being said, almost all of its potential lies in the Idea finisher. The Dev cost reduction. Currently, the META for EU4 is to stack as many dev cost modifiers as possible, in order to develop your provinces as cheaply as possible. 

The reason for this? Almost exponential-like growth. At least for developing production and manpower. 

You see, production development affects many things. From the goods produced, to the production income itself. And is in turn affected by those things as well. 

However, goods produced also affects trade, which is the most valuable of the income types, by far. As a result, developing production instead of tax will allow you to increase your income many, many times higher, and faster, than if you just increased the tax in your provinces.

Manpower is self-explanatory. The more of it you have, the more wars you can fight, and the longer you can fight for. Eventually, the amount of manpower you can get per month will be higher than the amount of manpower you lose per month. 

And when you reach that point, which can be done much faster by following the META rather than just blobbing, you’ve basically already won the game.

So, simply because of the insane potential of this Idea Group, it comes in at the number 3 spot, despite my own personal dislike of it. Funnily enough, for an Idea Group with such potential, its policies are hit-or-miss. 

Some, are very powerful. Others are not. It really depends on what you’re trying to accomplish.

In summary, the most important things this idea gives you are:

-A bit better overall economy

-Less inflation and better loans

-Insanely cheap development costs

Idea group bonuses and notable policies:

• +10% National tax modifier
• -10% Construction cost
• +0.10 Yearly inflation reduction
• -0.5 Interest per annum
• -0.05 Monthly autonomy change
• -5% Lands maintenance modifier
• +10% Production efficiency

      Finisher: -20% Development cost
      Good policy combo: Eco+Quantity +10% Force limit, -10% Development cost

 

2) Administrative

It’s safe to say that Administrative is an Idea Group that you have very little reason not to pick, and a lot of reasons to pick.

Sure, the bonuses it has for mercenaries aren’t the best thing in the world, unless you regularly use mercenaries. Or even play as a nation that’s dedicated to using mercenaries, like Switzerland. But the other bonuses are very much worth these subpar improvements.

Cheaper core creation cost might not seem like that big of a deal, but like province warscore cost from Diplomatic, it’s actually incredibly powerful. Think of how many provinces there are in the game. Now think of how many provinces you’re likely to conquer in any given campaign. 

That’s a lot of provinces, right? Well, imagine all of the thousands of admin points you’ll need to spend coring them. Now, if that number doesn’t make you lightheaded, I don’t know what will.

Thankfully, in incomes Admin Ideas with its 25% cheaper cores. That big number you just came up with? You can just slash a quarter off of it with this idea group. 

Hell, all you’ll need to do to unlock this insanely efficient bonus is reach the 2nd idea! It’s not even a finisher! 

Of course, if you combined this bonus with another core creation cost reduction from certain nations’ national ideas. As well as bonuses from certain religions and other mechanics, such as the HRE or MoH, you can core provinces for less than a quarter of their original price. And that’s not even considering the further reductions admin efficiency and absolutism give you!

Of course, cheaper cores aren’t the only thing this modifier interacts with. In fact, you’ll also get faster cores. Coring a province outside of your culture group without a claim takes about 3 years. 

Stacking enough core creation cost modifiers, you can bring that number down to 6 months. To put this into perspective, that might not even be long enough to trigger any overextension events!

And of course, the finisher for the group is absolutely essential if you’re planning on conquering any significant amount of land. The extra governing capacity is absolutely incredible, and it only gets better with time, since it’s a percentage-based modifier. So there is always a time to pick this idea, be it the early game, or the late game.

Finally, the policies for this Idea Group are for the most part solid, with a few stand-out exceptions.

In summary, the most important things this idea gives you are:

-Cheaper and faster cores

-Improved mercenaries

-A larger buffer before you start suffering the consequences of reckless expansion

Idea group bonuses and notable policies:

• -10% Mercenary cost
• -25% Core-creation cost
• -15% Mercenary maintenance
• -0.5 Interest per annum
• +25% Mercenary manpower
• +1 Possible advisors
• -10% Administrative technology cost

      Finisher: +25% Governing capacity modifier
      Good policy combo: Admin+Influence -20% Diplomatic annexation cost

 

1) Quantity

If there is any Idea Group that I would deem absolutely necessary, it would be this one.

Quantity does exactly what it says, it increases your army size. Be that the maximum amount of manpower that you can have in reserve, or the amount of manpower replenish per month. Or, even the amount of manpower you can have in the field. 

The business of this Idea Group is manpower, and business, as they say, is booming.

Of course, your manpower isn’t the only thing that benefits from this Idea Group. Cheaper troops, allowing you to field more of them for less of a price. As well as less attrition, which helps preserve your vast pool of fresh recruits. 

To even better garrisons, and higher supplied provinces, allowing for larger armies to exist without starving.

These are all great buffs, but do they really help make Quantity the best Idea Group? Well, on their own, kind of. However, when put together, as well as when you really break down the game to its fundamentals. Yes, they very much do.

As previously said, the most fun thing to do in the game is to wage war. It doesn’t really matter what kind of war it is. It can be a war of conquest or liberation. 

A trade dispute or subjugation. Or even spreading the revolution, or containing it. The fact of the matter is, the “fun” is in fighting, and having enough manpower to get you through your many conflicts is a must. 

After all, nobody likes running out of the resource they need most to win. If I were to use a historical example, one of the reasons the Roman Empire fell was because of a lack of manpower to fend off the various invaders. So, just imagine what the world would’ve been like if Rome had enough manpower to survive? 

Similarly, having enough manpower is vital for any nation, both big and small, in EU4.

There is also, funnily enough, a hidden diplomatic bonus to Quantity. Rather, for some reason, AI nations value army size significantly more than army quality. And as a result, they just might end up being too afraid to attack you if they think that you have so much more troops than them, even if, quality-wise, they would beat you in a straight fight.

So, for being an Idea Group that gives such an essential bonus, as well as letting you experience the best part of the game itself more fully, Quantity easily earns the top spot on this list. 

Policy-wise, the Idea Group is OK. It does have a few downright broken overpowered modifiers, but for the most part, the bonuses are fairly standard.

In summary, the most important things this idea gives you are:

-Literally the ability to play the game

-Unexpected diplomatic assistance

Idea group bonuses and notable policies:

• +50% National manpower modifier
• +20% Manpower recovery speed
• −10% Regiment cost
• −5% Land maintenance modifier
• +33% National supply limit modifier
• +25% Garrison size
• −10% Land attrition

      Finisher: +50% Land force limit modifier
      Good policy combo: Quantity+Religious +10% Morale of Armies, +5% Army Morale Recovery Speed

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