In 19 century it is considered as time of change becoz 
in the 18 century people of europe had no idea of nationalism and nation state  napoleon and his wars french revolution gave idea of nationalism 
the devolpment of nationalism did notcome abhout only throgh wars and teritorial expantion ROMANTISM was  a cultural movement which soght to devolop a perticular form of nationalist sentiment 
romantic artists and poets focused on emotions and mystical feelings  hope it helps and plz pick as best