Among major causes of both World War I and II, which is often considered the most significant?

Extreme nationalism is often considered the most significant cause of both World War I and II because it fostered an environment of hostility and competition among nations. During World War I, the fervent pride and loyalty individuals felt towards their nations contributed to escalating tensions, particularly in Europe, leading to the outbreak of war following the assassination of Archduke Franz Ferdinand. Nationalistic sentiments drove countries to form contentious alliances and stirred desires for territorial expansion, which were key factors in the global conflict.

In World War II, extreme nationalism played a crucial role as well, particularly in the rise of totalitarian regimes such as Nazi Germany, where Adolf Hitler's nationalist rhetoric promoted aggressive expansionism. This nationalism not only justified the invasion of other countries but also encouraged the idea of racial superiority, leading to horrific consequences. Thus, it can be understood that extreme nationalism served as a catalyst for both wars, shaping the political landscape and leading to violent confrontations.

While military buildup and aggression, political unrest, and agreements and alliances contributed to the wars, they are often seen as manifestations or byproducts of the underlying extreme nationalist sentiments that catalyzed these global conflicts.