Wikipedia
Anti-nationalism denotes the sentiments associated with an opposition to nationalism. Some anti-nationalists are humanitarians or humanists who pursue an idealist view of world community, and self-identify as world citizens. They often claim to reject chauvinism, jingoism and militarism, and desire peace rather than perpetual conflict, which they claim can be rooted in nationalism. The imposition of nationalism as a belief or identity system, particularly when in conflict with more established and self-sustaining identity choices, often based on freely chosen religious or cultural beliefs and practices can be understood to undermine the legitimacy of territory-based nationalism. They sometimes do not necessarily oppose the concepts of countries, nation states, national boundaries, cultural preservation, and identity politics.
Some anti-nationalists oppose all types of nationalism, including ethnic nationalism among oppressed minority groups. This strain of anti-nationalism typically advocates the elimination of national boundaries. Variations on this theme are often seen in Marxist theory. Marx and Engels rejected nationalism as a whole, stating that, "the working men have no country". More recently, certain groups descended from the Maoist tradition of Marxism have moved towards this fiercely anti-nationalist stance in a different way than Trotskyists, saying that, although it may be a painful and unpopular position to hear, ultimately opposing all nationalism strengthens proletarian internationalism. Many Trotskyists, however, such as Chris Harman, were critical of nationalism while advocating support for what they saw as progressive national struggles.