What is nationalism in classical music?

For example, it is using some traditional/national motifs in compositions. Chopin, for example, composed a lot of mazurkas and used several hints of Polish folk music in his compositions.

Nationalism in music began in the 19th century, particularly in areas which were subjected to the Austro-Hungarian and Russian Empires. It was a way of establishing a national identity. So we have Chopin in Poland who used traditional dance forms - the mazurka, the polonaise. In Bohemia (Czechoslovakia etc.) there was Smetana, who used dance forms and wrote about his country - the set of tone poems called 'My Vlast' or 'my country'. he also wrote operas on national themes - Libuse for example, and about popular culture - The Bartered Bride. He was followed by Dvorak who again used dance forms - his set of Slavonic Dances, Dumky piano trio etc. There were nationalists in Russia who wrote about national themes again. Rimsky-Korsakov wrote operas based on folk tales - The Legend of the Invisible City of Kitezh is an example. Borodin (Prince Igor) and Mussorsky (Boris Godunov) are others. Nationalism spread to England and Scotland (Vaughan-Williams, Hamish MacCunn) and even to America. In some ways Copland could be regarded as a nationalist with pieces like Appalacian Spring