In 1938 the Nazis altered about one-third of the toponyms of the area, eliminating, Germanizing, or simplifying a number of Old Prussian names, as well as those Polish or Lithuanian names originating from colonists and refugees to Prussia during and after the Protestant Reformation. More than 1,500 places were ordered to be renamed by 16 July 1938 following a decree issued by Gauleiter and Oberpräsident Erich Koch and initiated by Adolf Hitler. Many who would not cooperate with the rulers of Nazi Germany were sent to concentration camps and held prisoner there until their death or liberation.

In what year did the Nazi's alter around one-third of the toponyms of the area?