The period leading up to World War I and World War II was characterized by rising tensions and the growing threat of war.
In the case of World War I, a complex system of alliances and rivalries between European powers, coupled with the arms race and the growing nationalism and imperialism, led to the outbreak of war.
The assassination of Archduke Franz Ferdinand of Austria-Hungary in 1914 was the spark that ignited the conflict, but underlying tensions had been simmering for years.
