When attacking and taking a province there is a chance of receiving a Spoils-of-War. Most spoils allow you to increase a characters IQ, War, or Charm while increasing their loyalty to the maximum. A few spoils provide other benefits such as fast recovery from illness or protection from being captured. When attacking and taking province 10 you can obtain a normal spoils-of-war every time until you have all of the normal spoils. AI controlled rulers do not receive spoils, so allowing an AI controlled ruler to take or occupy province 10 will allow a player controlled ruler to retake the province for another spoil.