Why did nationalism had to do with the start of the Great War?

Nationalism was a prominent force in early 20th century Europe and a significant cause of World War I. Nationalism is an intense form of patriotism or loyalty to one’s country. Nationalists exaggerate the importance or virtues of their home country, placing its interests above those of other nations. The effects of this growing nationalism were an inflated confidence in one’s nation, its government, economy and military power. Many nationalists also became blind to the faults of their own nation. In matters of foreign affairs or global competition, they were convinced that their country was fair, righteous and beyond fault.

In contrast, nationalists criticised rival nations to the point of demonisation, caricaturing them as aggressive, scheming, deceitful, backward or uncivilised. Nationalist press reports convinced many readers the interests of their country were being threatened by the plotting, scheming and hungry imperialism of its rivals.

Idon't think any of em are right, you need to add the number of what paragraph you got your citation from