Simplify the following text for a Grade 14 native English-speaking person.
Original: There were other crusades against Islamic forces in southern Spain , southern Italy , and Sicily , as well as the campaigns of Teutonic knights against pagan strongholds in Eastern Europe , and ( to a much lesser extent ) crusades within Christendom against heretical groups .
Simplified: There were other crusades against Islamic forces in southern Spain , southern Italy , and Sicily , as well as the campaigns of Teutonic knights against pagan strongholds in Northeastern Europe ( see Northern Crusades ) .