What did william the conqueror achieve?

He was the duke of the Northern section of France called Normandy. He was also in line to be the English King, but him an his brother had fought over the throne and William had won.  He was known for his victory at the Battle of Hastings.  He built many castles throughout England to gain control and they were used as bases and fortresses. He also commissioned the "Dooms Day" book, which contained every citizen of England, which is must like our national census of today.  He also created the Feudal System, meaning the richer you are, the more land you get. 

Mussolini launched a powerful navy