*the options*
World War I is the event that really started the 20th century, putting an end to what was conventionally called Belle Epoque - 1871-1914: a period in which the great European powers did not go to war with each other and the bourgeoisie lived its time of greatest fastigio, thanks to the expansion of imperialist capitalism and the exploitation imposed on the proletariat.
There was a reallocation of positions of the European powers. The result was the formation of two opposing blocks:
Triple Alliance: Germany, Austria-Hungary and Italy. The latter joined Germany in retaliation against France, which had frustrated the Italian intention to conquer Tunisia. But the fact that Austria-Hungary was part of the bloc bothered Italians, due to the issue of "irredent cities".
Triple Entente: England (or rather, Great Britain), France and Russia. This name comes from Entente Cordiale (“Cordial Understanding”) - the way the French government defined its approach to England, of whom France was a traditional opponent.
The period that preceded the outbreak of World War I is known as Armed Peace, because the great powers, convinced of the inevitability of the conflict and even wishing for it, accelerated their war preparations (except Italy, which was not quite sure of the would do). On two occasions, in 1905 and 1911, Germany provoked France about Morocco, but the crises were overcome.
