Several european nations formed the european community in 1957 to

allow for the movement of goods, services, and people across borders and to eliminate tariffs among member nations

Alliances were an important feature of the international system on the eve of World War I. The formation of rival blocs of Great Powers has previously considered a major cause of the outbreak of war in 1914. The alliances system meant that a local conflict could easily result into an intimidating global one. Nationalism was a great cause of World War one because of countries being greedy and not negotiating.

Explanation: