"Nationalism is one of the VARIOUS METHODS proposed for the attainment of nation's welfare. . . . It is the aim of nationalism to promote the well-being of the whole nation or of some groups of its citizens by inflicting harm on foreigners. The outstanding method of modern nationalism is discrimination against foreigners in the economic sphere. Foreign goods are excluded from the domestic market or admitted only after the payment of an import duty. Foreign labor is barred from competition in the domestic labor market. Foreign capital is liable to confiscation. This economic nationalism must result in war whenever those injured believe that they are strong enough to brush away by armed violent action the measures detrimental to their own welfare."
Patriotism on the other hand is different from nationalism. It "is the ZEAL for one’s own nation’s welfare, flowering, and freedom." Patriots "recommend free trade, international division of labor, good will, and peace among the nations, not for the sake of foreigners but for the promotion of the happiness of their own nation."
Source: Ludwig von Mises, Omnipotent Government, 1944, p. 2