EU4: How Do You Get a Personal Union?

Personal Unions (PU) are two countries ruled by the same monarch. They are a result of royal marriages and years of political maneuvering. Common PUs are also highly dependent on RNG, as opposed to scripted PUs formed by missions and events. Scripted ones are exclusive to certain countries only.

As such, this guide will focus on getting PUs the regular way — by spreading your dynasty. This is usually a two-step process:

1. Place a member of your dynasty on your target’s throne
2. Keep preserving your dynasty’s rulership of the target until it results in a Personal Union

Before anything else though, PUs are only available to Christian monarchies. This includes the following denominations:

• Catholic
• Orthodox
• Coptic
• Protestant
• Reformed
• Anglican
• Hussite

This means that mostly the Europeans can benefit from this mechanic. They’re also your only potential prospects for a PU.

For non-Europeans, they first need to convert to Christianity. Then they must reform their government to a monarchy. Even after that, their PU success rate would be abysmal. In the first place, they’ll find it hard to establish marriages due to opinion penalties. Those are usually because of distance and cultural differences. So it’s rarely worth it for nations outside of Europe to get into the PU game.

Quick Tips for Beginners

Tip #1: Check the Disputed Succession notification often

This is among your notifications on the top-left of your screen.

Hovering over it shows you all countries that have no heir. Those highlighted in green are your marriage partners that can turn into PUs.

It also displays the ages of the rulers. In the game’s hidden calculations, rulers over the age of 30 have a reduced chance of getting an heir.

The ones over 40 also have twice the likelihood of dying, which gets higher per decade. So if you don’t want to wait too long for your PU-farming efforts to bear fruit, marry the elderly. The riper, the better. (Don’t do this in real life though. Please respect your elders.)

The notification also includes the prestige stat of the countries. But more on that later in the actual PU guide below.

Tip #2: Hover over your ruler’s name in the Court tab to view your dynastic links

This makes a tooltip appear that shows you these key details:

Of these details, you’ll want to monitor the successors to your marriage partners’ thrones. This data can change, usually when their heir dies or a more powerful dynasty becomes a claimant.

What you should look out for is when it says “A noble from House X succeeds to the throne”.

The variable X stands in for the name of the eligible dynasty.

• If it’s your dynasty, then you only need to wait for your target’s ruler to die.
• If it’s someone else’s, then you may still be able to overtake their claim. You do this by having a higher development and prestige than them.

Tip #3: Hover over your target’s ruler in their Diplomacy tab to check their status

This ties in to the previous tip, which only shows your own progress in the PU race.

For this particular tip, you’re trying to look into your target’s own royal marriages. They may be married to a more powerful dynasty, which could become a hindrance to your plans.

Their presence as a third party can spark a Succession War if your target dies heirless. In that case, you’ll be able to prepare or react accordingly.

Tip #4: Refer to the Dynastic Map Mode

You can get a bird’s-eye view over the spread of your dynasty with this map mode.

Granted this is not as detailed as the other tips here. But it does let you compare your dynasty with your competitors at a glance.

Tip #5: Watch out for Pretender Rebels

Pretender rebels will try to install a new ruler on your throne.

They’re often a minor noble house within your country. If you allow them to succeed, then they’ll also replace your ruling dynasty with the pretender’s noble house.

However, only your country will be affected, as rebels are an internal problem. Other countries where you’ve planted your previous dynasty will remain the same.

In other words: you’ll be playing the PU game all over again with your new dynasty. So don’t let that happen and crush all pretender rebels.

How To Get a Personal Union

I. Royal Marriages

It’s highly recommended to set up royal marriages with as many countries as you can.

Trying to get PUs is a numbers game. Having many partners at once increases your likelihood of getting one down the line.

Royal marriages can be classified into two types. These determine how long it takes to yield a PU. Note that you can only see the rulers, spouses, and heirs of your dynasty. All other insignificant members are mere lines of code in the background.

1. Direct royal marriages between two countries’ rulers or heirs

This means that one country’s male ruler is married to another country’s female ruler. This form always results in a Personal Union, since both rulers’ successor is their child.

You only need to wait for the rulers to die and pass on their titles to their child.

You won’t have to do any extra steps to get a PU. However, female rulers are rare, making this type of marriage also rare.

There’s also a variation where the marriage is between the rulers’ children. This doesn’t always turn into a PU though, as the maternal side may have a male heir. Most monarchies in EU4 follow the male-preference primogeniture law. This means females can only inherit their parent’s throne if they have no brothers.

2. Indirect royal marriages between members of two countries’ dynasties

If both rulers are ineligible, then the game creates invisible relatives as substitutes.

They only get names if they rise to power on your target’s throne. That can happen when your target dies heirless.

II. Succeeding the Throne

Dynastic Change

When your target’s ruler dies without an heir, your dynasty has a chance to take over their throne.

This can sometimes result in an immediate PU, usually in the case of a direct royal marriage.

If it’s your relative, then you’ll at least get your dynasty on your target’s throne. Should that happen, then you already have one foot in the door.

Next you’ll have to wait until your relative dies heirless and you become the successor to their throne. The time needed for this is entirely based on luck. If your relative does gain an heir, then you need to wait longer until their descendants die out.

Succession War

Almost all monarchies have multiple royal marriages with several countries. But only the one with the highest development and prestige gets the PU over the target.

As soon as that happens, an event will give the losers an option to contest the union. If at least one chooses to do so, it’ll automatically trigger a Succession War.

If you’re the one that initiated the war, you can steal the PU by prevailing over the rightful successor. Otherwise, the defender can simply settle for a white peace and retain the PU.

The logic here is that the defender has already assumed control of the target country. So if someone disputes it, the defender is merely repelling the ones who are trying to take it away.

“Claim on Throne” Casus Belli

The PU process may take a long time, but you do have the option to expedite it.

You can do this by pressing the “Claim Throne” Dynastic action in the Diplomacy screen. It’s available to you if:

• You have a royal marriage with your target
• Your target already has your ruling dynasty
• Your target either has no heir or their heir has a weak claim
• You have a higher prestige than your target

This action gives you a “Claim on Throne” CB, which you can use to declare war on your target. Winning that war lets you enforce a PU over them.

However, this shortcut does have several penalties:

• -20 Prestige
• -100 Relations with the target country
• -25 Trust with the target
• -50 Relations with your other royal marriage partners

In other words, your PU partner will likely be disloyal and rebellious. You’ll also damage your chances with the rest of your marriage partners. Consider those risks first before you use the “Claim Throne” action.