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Get in good with them, fuck one of their daughters (metaphorically, don't actually do that they'll hang you).
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Join a faction, perhaps a small faction, and help them take fiefs.
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I've seen France field 3000 men, don't try to 1v1 them
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You can't go from free rider to King and if by some miracle of invention you did take a castle or town (perhaps one that had been recently taken and left), then you would be curb stomped by another faction.
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