Googling that phrase, the first hit I get is Fascism, not Nationalism.
https://encyclopedia.ushmm.org/content/en/article/fascism-1
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Definition and Beliefs
Fascism is an ultranationalist, authoritarian political philosophy. It combines elements of nationalism, militarism, economic self-sufficiency, and totalitarianism. It opposes communism, socialism, pluralism, individual rights and equality, and democratic government.
Fascism places the importance of the nation above all else. The unity of the national community is prioritized above the rights of individuals. This leads to an intense interest in defining which groups belong or do not belong to the national body. Fascism is characterized by:
strident, often exclusionary nationalism
fixation with national decline (real or perceived) and threats to the existence of the national community
embrace of paramilitarism
These two ideas seem to have become synonymous in the minds of most people, but academically they are distinct.