Eurpoean Imperialism, where a country extends its influence and culture through trade, diplomacy, and military, had been steadily growing since the late 1400's, when countries started to acquire colonies. Colonies eventually became part of empires, Britain's being the largest and most affluent in the 1800's. Before empires were built, however, the forces of Nationalism within various European states caused them to attempt to expand borders and commerce at the expense of their neighbors. The rise of the British Empire in the mid 1800's and earlier, the expansion of France under Napoleon in the late 1700's, induced other European powers, notably Germany and Italy, to consolidate and develop their own brand of Nationalism, then acquire their own colonies as their own form of Imperialism. This competition among the major European Powers, inside and outside of Europe, finally resulted in major conflict in 1914 causing the First World War. See more at the link:
European Imperialism was directly linked with the rise of industrialization in those nations. The need for raw materials and a generally more aggressive political landscape fueled the fires of conflict. Many European nations were uniting along cultural or ethnic lines, such as Germany and Italy. People uniting as Italians, for example, instead of as Romans or Venitians, created nationalistic societies that valued patriotism and service to one's country. The economically successful countries, i.e. Britain, Germany, and France had the power and means to impose their will on others without fear of repercussions.