Gradually

"[W]hen the resolution of enslaving America was formed in Great Britain, the British Parliament was advised by an artful man, - who was governor of Pennsylvania, to disarm the people; that it was the best and most effectual way to enslave them; but that they should not do it openly, but weaken them, and let them sink gradually, by totally disusing and neglecting the militia."
--George Mason, speech in the Virginia Ratifying Convention, 14 June 1778