What was the effect of nationalism on countries Ww1?

Nationalism played a significant role in the lead-up to World War I by fostering intense pride and competition among nations. It heightened tensions, particularly in regions like the Balkans, where ethnic groups sought independence or unification, leading to conflicts such as the assassination of Archduke Franz Ferdinand. Nationalist fervor also drove countries to form alliances and pursue militarization, ultimately contributing to the war's outbreak and the escalation of hostilities across Europe. This fervent sense of national identity often overshadowed diplomatic solutions, making conflict seem more appealing or justified.