Why did ultra-nationalism help to cause world war 1?

Ultra-nationalism fueled tensions among European nations by promoting the idea that one's nation was superior to others, leading to rivalries and conflicts over territory and influence. It contributed to the assassination of Archduke Franz Ferdinand, as nationalist movements sought independence and recognition for their ethnic groups. This fervent nationalism created an environment where countries were more willing to engage in militaristic actions and alliances, ultimately escalating into World War I.