Knights don't really capture fields on purpose, if it happens, it happens. Knights destroy fields on purpose, usually in a frenzied bloodlust until, for one reason or another, there are no more defenders. Then we get bored and move on, weather the field gets captured or not is incidental. It usually happens when Knights who have chased prey back to ack become cross enough to de-ack. When the base is de-acked the call goes out and Knights will gather like piranha at a cattle river crossing.
Rooks are mongols, bishops are romans. Knights are Vikings, we don't come for your land, and after we get our fill we take our ships home.
From the fury of the Knights deliver us O Lord.