What's the navy got to do with anything? They can't do much at all to land unless it's like, on the beach. And if you didn't notice, Therral was made to be self sufficient in Bullis with all soldiers raised; with no soldiers raised, he could become one of the richest Lord's in Lundlands.

P.S. - killing any people of Therral will destroy the self sufficiency, and they have enough faith in Solterra that they won't just let people take their homes.