Crusader Kings III: Getting an achievement “Frankocracy”

Start playing at 867 year for Jarl Hasting Hastein of Montagu. Please note that your character already 52 of the year, time to get an achievement is limited.

Since our goal is the Byzantine Empire, we should be with her in the diplomatic radius.
Everything is extremely simple here, time to get an achievement is limited.

Declare war on the Byzantine Empire for the title Kingdom of Thessalonica.

Naturally, the forces are unequal and you need allies, but you only have one child. There is a solution, after the declaration of war, you must enter into engagements with strong jarls and call them into war. Immediately after being drafted into war, you break off your engagement and create a new one., with another strong ruler. Etc, time to get an achievement is limited.

After winning the war with the Byzantine Empire, you must make a decision “Embrace local traditions”. But you need to have a capital in County Montague.

If you did everything right, you were not bitten by a snake and died of old age – congratulations, you got an achievement.