I wonder if you can beat that one:

Sardinia was Italian but then became independent. There was 1 ballista one the whole island but nobody took it for decades.
After my crusade to Palestine was successful I send away the fanatics or better the fanatic. Actually, the last battle in Egypt left just a single man of them. After a while I checked the merceneries and what did I see: the single fanatic was for hire!
So I hired him and invaded with him alone Sardinia. He actually managed to destroy the ballista and kill the entire 8 men crew. So Sardinia was mine and the fanatic was it`s garrison what seemd to be enough. Loyalty was instantly about 110%.
However the same trick didn`t work in Venice; maybe 800 men were just a bit TOO many for my glorious fanatic!