Free city campaign - playing tall: how to conquer Boriken without losing free city status

[byebytoad]

As per title, I'm playing a campaign as a free city (Hamburg with custom ideas) .
I'm playing tall and i don't want to lose my free city status and so I don't want to conquer directly any city.

My goal is to acquire 1-city vassals (8-9 of them) placed in strategic location (center of trades).
So far I have Riga, Gotland, Holstein, Lubeck, Rugen, Bremen.
Soon I plan to add Danzig.

I'm also interested in getting control of Boriken , mostly for its monument (30% naval force limit to its overlord).
To not to lose the free city status, I'd need to turn any new conquest into a vassal before the end of the month.
What would be the best way to make Boriken a vassall before the year 1520?

 

[Nwaij]

Tall order you have there! I'd guess the best option might be to force vassalize some hapless native nearby (for coring range), wait for someone else to colonize it, declar war on said someone, transfer occupation to your native vassal and claim it in the peace deal. Consider making sure said vassal to ontain 4 more provinces in the same way and annexing him eventually - colonial nations are a thing!

(Good Luck, you will need it...)