A vassal is a semi-independent nation that owes allegiance to a country, often much more powerful than the vassal. The vassal offers regular financial tribute and military assistance, and in return receives protection. - EU IV Wiki.


But vassals are much more than that.
Vassals are you loyal dogs which will do anything for you.
1) Core provinces
2) Help out Wars & Sieges
3) Pay you money & Develop provinces
4) Convert religion
5) Hunt & Put Down Rebels
6) Fabricate Claims and/or Give you a powerful Reconquest CB
7) Diplo Annexation is Cheaper
and...
Die for you until they are disloyal, then they try to kill you.

Since this guide is about World Conquests (WCs) & Ultra blob tips, the main focus will be on #1, 2, 3, 4, 6, 7

In a World Conquest, ever since the introduction of states & territories, monarch points have ceased to be a problem.
Barring Aggressive Expansion & Coalition obstacle (ie: you are Ottomans that can expand in all directions), WC is all about the speed of conquests, how much you can eat and core and remain stable.


And so, Overextension becomes the largest demon in blobbing.
Every 1 dev gives 1 OE, which means at any possible timeframe you can at most have 100 dev of uncored provinces before Admin Efficiency comes into play.
At 100% OE, your nation will get +5 National Unrest, lower diplomatic rep, etc.
And we all know going over 100% OE gives a bunch of nasty bad events, spawn rebels, further destabilizing your country, and we dont want that.

Coring a province yourself takes 3 years/36 months, if your nation do NOT have ideas that reduce coring cost (hence time). (Ottomans Millets idea reduces core time by 33%)
The only way to reduce it is taking Admin Idea 2: Adaptability (-25% cost and time)
Even so it takes 27 months for fully core 100% Overextension.

If you have claims then core time gets -10% modifier (But you can't fib that many claims)
If the provinces are in the same cultural group as you then it's -50% (reasonably fast)

But even then, you might run out of admin points.
So what do you do? Use Vassals.

This is me eating up India as fast as possible by using 3 vassals for absorption (400 AE cap).

Vassals are powerful.
With the 1.18 Tech overhaul, you can potentially use vassals in China & India too.
With Art of War you can transfer occupation of provinces to your vassals.
With Cossacks you can grant vassals your provinces directly.


As mentioned, upon hitting the OE cap of 99.9% yourself, you can't really core any province yourself anymore.
But with a vassal, you can potentially grant them another 100% OE worth of provinces and let them core it, which gives you a capacity of 200 Overextension, which scales with the amount of vassals you can feed.

And as a Bonus:
1) If they have a core reduction National Idea (ie: Karaman, Hordes, Client States), then they get lower admin core cost for them, and also speed up their coring process, and let you feed another batch to them quickly.

2) if they are in the same culture group as the conquered provinces,
ie: Feed Tver/Novgorod with Russian culture, Feed Persia with Iranian culture
then they get -50% core time, as well as lower unrest for accepted culture.

Important part:
You get a core on where they have a core on. That is, you will only get territorial core if they only have a territorial core there.
But most/99% vassals will fully core all the lands they get unless they are out of states (unlikely), so upon annexation you can get a FULL CORE on all their lands.
Hence it is my core strategy to feed vassals the highly developed provinces that I intend to make states later (ie: Anatolia, Moscow, Italy/Naples region)

Vassals will do whatever you want them to do, unlike the stupid AI allies that run around doing nothing.

1) Vassals will always be called to war with you.

2) Depending on the military focus YOU SET, they can help you in battle, attach to your stack, siege down forts on their own, etc.

3) Don't think OPM vassals are useless.
Each nation has its own manpower pool of base 10000, and base tax income and base force-limit.
That means potentially by making a number of vassals, your combined manpower pool and army size (force limit) can get much larger than you can afford (money) on your own.
And when AI vassals run out of manpower, they will field more mercs even when that means taking loans.


And best part - Once you annexed them you get ALL their army, including mercs, but not their loans. You are expanding your army without spending any cash or manpower.

As said in the last chapter, vassals are just like any other independent country, they get money from tax, production, trade.

And they will make your rich in turn:
1) They will develop lands if they have spare monarch points!

2) They will build buildings if they have money, so you can get extra tax, production & manpower.

3) They will pay you a little sum of money each month from their taxation income. This can be increased by taking certain ideas.

This is an important part of vassal feeding.


Upon conquering a foreign province, a number of factors contribute to Unrest.
1 - Religion
Unless you have taken Humanist idea, each point of intolerance gives +1.25 Unrest, and contribute to less Religion Unity and that gives additional National Unrest.
If you take Religion ideas, then you still have to convert them yourself but that can't be done while coring is in progress.

2 - Culture
Non accepted culture gives +2 Unrest.

3 - Separatism
Unless you have Humanist, it starts with +15 Unrest, and gradually decrease in 30 years.

4 - Overextension
OE gives National Unrest, scales up to +5 Unrest at 100% OE.

So vassals become a natural choice for the first two problems.
This is my favourite - Lets say you make Karaman a vassal, Sunni & Turkish culture, and you feed them entire Ottomans' Anatolia.
They will core ultra fast to suck up the Overextension (-20% from NI, -25% from Admin, -50% time from culture group), and they will experience much less unrest from correct religion & same culture.
Separatism will be beaten down by raising autonomy.

Important: Therefore it is important to feed normal vassal correct religion & cultural group provinces.
There are Exceptions though:
1) Hordes - Fast & Cheap coring (especially with Admin ideas), less separatism & unrest from NI (Manchu horde is insanely good to eat China)
2) Religious vassals - Bulgaria, Byzantine, or vassals with Religious Ideas that gives bonus to religion conversion, they can suck up wrong religion provinces and convert them for you. (except Religious Zeal)

CBs, most important part of the game before Imperialism or getting Deus Vult.


Usually in early stage of World Conquest, you want to minimize AE gain to prevent coalitions, as well as speeding up conquest/build up speed.
Reconquest CB is your friend.

There are opportunities when a huge nation with lots of cores got beaten down to OPM, or you can release out of nowhere. (ie: Novgorod, Persia)
It's simple, just do a war against them, fully annex them (or force vassalize if it's not possible), then release/spit them out as your dependency and you can use their cores for a Reconquest CB,

It will give tiny bit of AE for a huge amount of lands; and you get 75% WS Cost for the cored provinces, so you can eat up more provinces than you can normally at 100% WS.

And of course that also comes with all the benefits of No Separatism and Local Autonomy or OE for the vassal.

When you are out of Reconquest CBs, the vassals will also fabricate claims on provinces you want, and on those whom you rival.

Normally you can lower liberty desire with:
1) Opinion of you
2) Diplomatic Reputation
3) Diplo tech

Usually in the early game you want to balance between
1) Filling out Influence idea (usually 1st idea group)
2) Teching up Diplo
3) Diplo point used on annexing vassals

I find the +2 diplo rep in the idea group & an advisor usually enough keep my vassals in check, and I only tech up diplo after I have completed Influence Ideas. (The discount on filling Ideas & Behind in tech is always good)

It is Very easy to manage if you have Cossacks.
Simply grant provinces to them that you want them to core. (Conquest/Deus Vult CB)
Usually that pushes their LD low enough you don't have to worry about them again.

Important:
Do NOT vassalize countries with massive AE malus against you.
It won't go away in years, it hurts your relationship & LD with them and you cant do anything about it, not even start the annexation.
Instead, FULL ANNEX and Release them.

Lastly, why is it a good idea to keep vassal annexing, other than gaining full cores?
The cost is much cheaper.


Before Admin Efficiency (It scales the same for both anyway) & Assume you have no discount on Core/Diplo-Annex in NIs:
Core cost:
Base - 10 admin points per development
Admin 2: -25%
= Fully Core 7.5/dev OR Territory 3.75/dev

Diplo Annex cost:
Base - 8 diplo points
Influence 3: -25%
Influence+Admin Policy: -20%
= Fully Core 4.4/dev

So you can see that, you are almost paying half the point cost for a fully cored province; and that works well with my strategy of vassal feeding high development regions that I can use as States later. For trash provinces, territorial cores are good enough.

And if you have high diplo rep, France gets +1 from Tradition, Austria gets +2 later, etc.
You can potentially annex vassals faster than coring provinces directly.
Base: +2, Same Religion: +1, and Diplo Rep.
I was burning -10 diplo points on every vassal I was annexing at the time.


I did a France World Conquest a while back.


And basically after you get Diplomatic Tech 23, unlocking Imperialism & Client States, Diplomatic technology is no longer relevant, and Liberty Desire for obsolete Diplo tech also is irrevelant because how big you are.

Thanks for reading.
Hope this helps clear things up and help in your future conquests.
Have fun!

If you like this guide and appreciate my work, please give it a thumb up, leave a comment; and check out my Youtube channel as a token of appreciation & support!! Thanks.

My other guides:
Dismantling HRE by 1600 Using League War - Early Germany
Vassals: Tips for World Conquests/Ultra Blob Expansions
The Three Mountains for Everyone (Guide/AAR)
Guide to do Easy WC/1-Faith, Revoke Privilegia in 1530
Guide to Stacking Discipline
Guide to Buildings & Income
100% Mercantilism & Venetian Sea
Guide to Keep 75% Autonomy for Territories After Raising it for Lower Unrest

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