Sentence:  The High Commissioner of the <WSD>Free City</WSD> of Danzig was a position established under the Peace Treaty of Versailles that concluded World War I. 
Meaning of the word marked with <WSD> tags:  Any of various types of city of Europe from classical to modern times, characterised by relative autonomy and/or being responsible only and directly to a king or emperor; a more modern city of such type, sometimes elsewhere than in Europe.