Dennis Showalter wrote about the King who reigned over what nation from 1740 to 1786?
Dennis Showalter:  He has written extensively on the wars of Frederick the Great, the , World War I, and World War II. Frederick the Great: Frederick II (German: "Friedrich" ; 24 January 171217 August 1786) was King of Prussia from 1740 until 1786, the longest reign of any Hohenzollern king.
Prussia