Using this strategy I was able to get the achievement 'The Navigator' without having any DLCs.
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- How to Byzantium in 1.25.
- A Basic Guide to Colonization.
- Quick & Simple Fix for Outdated Mods.
First of all, here is what you should do before unpausing after starting an ironman game as Portugal.
- Ask Castille for an alliance.
- Break your alliance with England.
- Delete all your heavy ships, you will not need them.
- Assign the explorer you start with to your light ships.
- Start building some transport ships so that you can transport all of your army later.
- Hire an administrative advisor.
- Delete your forts, you will not need them.
Exploration and Diplomacy
After that, send your light ships south to explore the coast of Africa until you can see the Kongo. Send your light ships back to Portugal and improve your relations with the Kongo. When your relations are good enough, ask for fleet basing rights and station your light ships with the explorer on the coast of the Kongo.
From there you should continue exploring the African coast until you can see Madagascar and Southern India. Improve your relations with someone on the East African coast (I am going to use Mombasa as an example here) and ask them for fleet basing rights, just like you did with the Kongo, and keep your light ships there.
Select the province Ceuta in Northern Africa and move your capitol to this province.
This is very important!
Assign a general to your army and use your transport ships to move your army to Mombasa. Wait for your army to replace the losses from transporting it and let your ships repair.
This is the part where you need to be a little lucky:
You need to declare a war with no Casus Belli on a small nation in Southern India and vassalise it, so attack a nation whithout alliances if possible. Improve your relations with your new vassal after the war. (keep in mind that the Maledives are no longer part of the India region since the Dharma update, so don't attack them)
Increase your stability occasionally when possible. Take Exploration as your first idea group!
After that, all you need is to get a core province on the coast of Madagascar:
- First, you need to vassalise any Madagascan nation, and then take a province next to it.
- The game will allow you to core a province if it is both bordering a vassal of you and on the same continent (Africa) as your capital. This is why you needed to move your capital to Ceuta!
Declare a war with no Casus Belli on the weakest nation in Madagascar.
- If it has an alliance with another nation which is on their border, vassalise that nation in a seperate peace deal first and then take a coastal province from the nation you attacked.
- If not, just vassalise it and declare another war on some Madagascan nation which is bordering your new vassal to get the coastal province you need.
Once you have done that, you are just a few minutes of waiting away from your achievement!
Send the colonist you get from the first Exploration idea to 'Ile de Bourbon' or 'Mauricius' (two islands east of Madagascar).
Get exploration idea 2 and 3 to increase your colonial range. While you are waiting for your colony to reach 1000 settlers, send an explorer into the pacific south of the Maledives and look for the island 'Hollavai'. Colonise that island as soon as possible and keep checking if you can integrate your vassal in Southern India already. If your relations are too low, improve them and send your vassal a gift. If you too far away, try inceasing your coring range. Start integrating your vassal immediately once possible.
With Hollhavai and the lands of your vassal you own all the required provinces for the achievement. The game year should be around 1490 - 1496, so time is not a difficulty if you attack early enough.
At that point you should get the achievement 'The Navigator'.