Ages 9 to 12 years Roman Conquests presents the history of the Roman army and describes some of the campaigns through which they conquered most of the known world. At its height, the Roman Empire stretched from Northern Britain to the shores of the Red Sea. Find out about the important events and people in Roman history and why the empire finally fell in the 5th century AD. Wars that Changed the World is a series of history books that looks at momentous wars, their causes and effects.