16th June 2017 Update:
I am leaving this old outdated guide up, but I sadly now do not personally recommend buying Crusader Kings 2. This is due to my disapproval with the direction of the game; with development time given to DLCs containing fantasy elements such as satanists and immortality, the addition of the unfun Shattered Retreat mechanic (even if you disable it, the core battle mechanics have changed to behave relevantly to it), and also mainly due to Paradox raising the prices of Crusader Kings 2 and many of their other games. Once again, I do not recommend buying this game. The original guide follows unaltered:

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This guide was made using version 2.1.1 of CK2.

This guide does not require semi-cheating such as "NK mode".

This guide requires you to play on Ironman mode, as you cannot get achievements otherwise.

You cannot use Ruler Designer as it disables achievements, even on Ironman mode.

The character of choice for this guide is Hasteinn Hasteining in The Old Gods start in 867. Hasteinn is the independent count of Nantes, located in North-West France. He initially follows Norse paganism, but you'll make him convert religion later.



The religion of choice for this guide is Buddhism. This is because Buddhism does not use the caste system. I attempted this same method before with Hinduism but found that entering yourself and your heirs into the caste system is expensive and time consuming. I have not attempted this with Jainism as I don't think Jainists have any decent casus belli to use against enemies.

This method involves some degree of luck and speed. While they won't end the game, there are a few random things that may happen that are major disadvantages. If any of these things happen before Hasteinn is a Buddhist petty King ruling in Britain, I recommend you restart the game and try again:

• Hasteinn dies.
  
• Your Buddhist concubine dies.
  
• Nantes or anywhere else you own gets a liberation or religious revolt.
  
• Somebody holy wars you.

There are a few things that I did, but are not entirely required, upon starting the game and before unpausing:

• Change the county laws so that City Levies are maximum.
  
• In Nantes make your Chancellor improve diplomatic relations and make your Marshal train troops, disallow both of them from leading armies.
  
• Make your Spymaster auto-stop plots, which is a just tickbox in the Intrigue menu.
  
• Take the 'Become a Paragon of Virtue' ambition, as it's the only one that's somewhat helpful to you.

Your first objective is to island hop your way to a place that's near the Indian ocean and will allow you to raid India. With the diplomatic range and there being no Suez canal for your ships to cross, you can't sail there directly.

After unpausing, declare a conquest war on the county of Cagliari in southern Sardinia:



Raise your levies and board them and the roughly 2000 event troops you start with onto your 40 ships. Sail to the west of Sardinia and order your troops to disembark on the neutral northern Sardinian county: Aborea - this is done to avoid the losses from an amphibious attack directly from the ships. After landing your troops, send your ships back to Nantes. Now order your troops to move south and attack Cagliari. You should easily win the war and take the county.

Your next target is Crete. Declare a conquest war on the county of Chandax:



Again, raise your levies and board them onto your ships. Before sailing to Crete, pick up your event troops from Sardinia with the same ships. Sail to Crete, disembark on an undefended county. Then send your ships back to Nantes. Wait until your troops' morale is high, then attack the Cretian army and siege down the target county.

After winning that war, you now have the diplomatic range to attack independent counties in Ethiopia:



Declare a conquest war on either Trinkitat or Assab, you only need one. Be sure whichever one you pick isn't already being attacked, as your war with them will inconclusively end if they are conquered by someone else. Yet again, raise your levies and board them and your event troops onto your ships. Then sail to the patch of sea called the Nile delta, south of Crete. Disembark your troops by ordering them to move to a coastal Egyptian county. Then order them to march across Egypt and besiege the enemy Ethiopian county.

Once you've won that war, disband your levies but keep your event troops in your newly conquested county.

You now need to acquire ships with which you can use to sail to India. Your diplomatic range is still too small to declare any wars on Indian nations, but you do not need to conquer any of India to get this achievement.

To get ships you will need to use the "Seize merchant ships" decision, which gives you 20 ships for 50 gold. You can only use this decision while at war. Declare a conquest war on the island of Socotra, south of Arabia:



Make sure Haesteinn is leading troops in your Ethiopian county and then choose the decision. 20 ships should appear in the Red Sea. Apparently the "Seize merchant ships" decision puts the ships closest to where your character is currently located (Credit to BlitzKrieg-Kjeld for pointing this out). This is why you must have Haesteinn leading troops in your Ethiopian county, otherwise he would be residing in Nantes and the seized ships would appear uselessly beside France.

The 20 boats can only hold 2000 men, be sure to have as close to 2000 troops as possible ready to board. If you have significantly less than 2000 troops in your Ethiopian county, reinforce them with levies from Nantes and your other counties.

Before boarding the seized merchant ships, set your troops to become raiders by selecting them and clicking the circular icon that looks like a torch and axe. Board the ships but do not sail to Socotra.

Use your ships to sail to India and begin raiding and sieging down any vulnerable Buddhist counties you can find. Your objective now is to capture a Buddhist woman, not to loot for gold. Use the religion map mode to check for Buddhist counties. Just raiding alone doesn't work, you need to win a siege in a county so that it gives you a chance of capturing a person after the siege - you just need to get lucky that you'll capture a Buddhist woman at this point. I think it took me about 5 years of raiding before I captured a Buddhist woman.

As a Norse pagan, you can sail up rivers, including the Ganges river. One recommended raiding target is the Mlechchha Kingdom, they're fairly small and shouldn't be able to raise too huge an army.



I don't recommend raiding the island of Sri Lanka, as in my experience it has a large amount of troops that can easily group up and destroy you. Also I could not get any Buddhist women from raiding the Maldives islands, but you may be more lucky.

Do not attempt to fight any large Indian army. They will almost certainly group up and out-number you while you're stuck fighting and they will win. It also just wastes your own men and time that could be spent raiding. If you see any hostile Indian army moving towards you, flee back to your ships.

The warscore for the conquest war against Socotra will gradually go lower and lower the longer you don't occupy Socotra. If you have not captured a Buddhist woman by the time the warscore gets to about minus 75%, send your army (be sure to toggle raid mode off) to siege and occupy Socotra. Ignore any peace offer that they send to you* and resume raiding India. Only end the Socotra war when you do not need the seized merchant ships anymore, as during peace they will automatically disband.

( *I'm unsure whether conquest wars are automatically ended for you after you hold 100% warscore for a long period of time, so that is why I don't advise occupying Socotra right away and getting 100% warscore before raiding. )

It isn't crucial to win the Socotra war as you're only doing it so you can seize the merchant ships. If you do win, do not create the Socotra Duchy / Petty Kingdom as you don't need it and it's just a waste of money.

Once you have captured an adult Buddhist woman (who isn't too likely to die soon such as being over 60 and having the maimed trait) and you have ended the Socotra war, move on to Part 3.

You should now be at peace.

Unless you think there's still a significant number of your event troops remaining, disband your event troops and all your levies. I personally decided it would be too time consuming to send them all the way back to Nantes.

If you have not done so already, take your captured female Buddhist prisoner as your concubine but do not convert to Buddhism yet. Taking her as a concubine now slightly lowers the chance of her dying as she won't get the 'in the dungeon' modifier.

Now give away every county you own other than Nantes to random courtiers so that they are independent and out of your realm, not your vassals. You do not want to be involved in any wars that those counties will inevitably be a part of soon. If you need random courtiers, invite Holy Men to your court using the decision in the Intrigue menu.

Now begins the conquest of Britannia. Choose a weak yet large petty Kingdom or Kingdom in Britain and select the Prepare Invasion option on the King/Queen. I chose the petty Kingdom of Wessex, but the circumstances may be different in your game and you may need to choose elsewhere. I don't recommend attacking Ireland first as they're just too weak and disunited, unless in your game somebody has managed to form the Kingdom of Ireland in which case that would be a good choice for invasion.

After selecting Prepare Invasion, it's up to you whether you wait around for two years to get any adventurer reinforcements or just immediately attack your target and use your levies and mercenaries. In my case I attacked Wessex after a month or two of waiting and hired two mercenary companies to help quickly assault and win sieges. I also made sure to occupy a large amount of the target, so that I'd receive many occupied counties and they wouldn't just become my vassals.

After winning the prepared invasion and before you give out any of the conquered territory, go to the Intrigue menu and choose the "Convert to Buddhism" decision, which is made available by the religion of your Buddhist concubine. After converting, select every vassal and courtier you have that has a positive opinion of you and demand them to convert to Buddhism. If they're important for whatever reason and won't convert, bribe them so they have a positive 35+ opinion of you and then demand them to convert.

It's up to you whether you change culture to Anglo-saxon or stay Norse, you can convert to Anglo-saxon by moving your capital from Nantes to an Anglo-saxon county and then selecting the change culture decision. In my case I stayed Norse and moved my capital to Middlesex which had turned Norse after the invasion.

After moving your capital to somewhere in Britain, give away Nantes to a random courtier and grant him independence.

Congratulations, you should now be a Buddhist petty King somewhere in Britain. Be sure to educate your son and heir Ragnarr and demand him to convert him to Buddhism if he reaches 16 and is still a Norse pagan. Use your Buddhist priest from your council to convert your capital county, which may be something very low like 2% or 3% chance a year, but it's really your only choice. To help with overall conversion, try to have as little non-Buddhist vassals in your realm as possible.



From this point onwards, it's largely simple. Try to create the relevant Kingdom in the area where your petty Kingdom is located in first, in my case it was the Kingdom of England, and then increase the crown authority to High and the succession law to Primogeniture. When you have the right crown authority, you can freely revoke non-Buddhists' titles.

(Remember that as you are initially a petty King with Gavelkind succession law, do not create more than one duchy as if you have more than one son the duchies will turn into independent petty Kingdoms upon your death. Only create more duchies when you have a real Kingdom.)

Holy war and de jure claim war everyone in Britain until you hold over 80% of the Britannia Empire's de jure land and hold 3 Kingdom titles - which will allow you to create the Empire. As a Buddhist, you can holy war your non-Buddhist neighbours for one county at a time. When expanding early on, only try and pick on countries that are already at war with someone else or are otherwise weak. I went after creating the Kingdom of England first, then Wales, and then Ireland.

During war, if you have enough Piety / Karma, hire the Buddhist holy order, they will make defensive and offensive holy wars much easier, so be sure to utilise them when possible. I was holy warred during Ragnarr's reign by Denmark, who owned Mercia, but I won with the help of the Holy Order.

In my case, I was at war or waiting for truces to expire with all my neighbours almost constantly. I managed to create the empire in 943 as Hasteinn's grandson, 76 years after the game started. It may take you shorter or longer depending on the circumstances.

Once you've created the Empire, unpause the game and after a short moment you should recieve the achievement.

Happy Buddhist Britannaing!