Simplify the following text for a Grade 4 native English-speaking person.
Original: Frederick William II ( ; 25 September 1744 -- 16 November 1797 ) was the King of Prussia , reigning from 1786 until his death .
Simplified: Frederick William II ( ; ( 25 September 1744 â `` 16 November 1797 ) was the fourth King of Prussia . He ruled from 1786 until his death .