The main causes of tensions between European countries before World War I were:
a) Nationalism: The desire for independence and self-determination among various ethnic groups, particularly in the Balkans, led to increased tensions, especially as nations like Austria-Hungary sought to maintain control over these regions.
b) Militarism: The arms race and glorification of military power created a climate where nations felt compelled to build up their armed forces and prepare for potential conflict, leading to heightened paranoia and mistrust among countries.
c) Alliances: The formation of secret treaties and military alliances, such as those between Germany and Austria-Hungary and the United Kingdom, Russia, and France, created an environment where a conflict involving one country could quickly escalate into a larger war.