national leader vs Iron Duke

national leader and Iron Duke both are nouns.

Word	Noun	Adjective	Verb	Adverb
national leader	Yes	No	No	No
Iron Duke	Yes	No	No	No

national leader (noun)	Iron Duke (noun)
a person who is a respected leader in national or international affairs	British general and statesman; he defeated Napoleon at Waterloo; subsequently served as Prime Minister (1769-1852)