Answer:
Yes, nationalism was a cause of World War 1 as the assassination of archduke Franz Ferdinand by Serbian nationalist Gavrilo Princip was one of the main reasons why the Austria-Hungary decided to wage war on Serbia.
Explanation:
Since the annexation of Bosnia and Herzegovina by Austria-Hungary in 1908 the situation on Balkan Peninsula was very tense.
Nationalism was rising, as no one wanted to accept the dominance of Austria-Hungary in the region.
Therefore, when Franz Ferdinand arrived in Sarajevo in 1914 this was seen as a provocation. Nationalist, led by the organization known as Young Bosnia decided to plan the assassination of the Austrian prince.
