Imperialism developed from the need for colonization by the European countries. They wanted to extend their reach onto other countries to gain more land, power and influence
Asian people whom came into contact with European empires responded in many different ways. China and Japan sought to restrict contact with Europeans. People from India and Vietnam were forced into accepting foreign/European influence as they had been conquered by outside powers.
Germany did not seek to extend its empire outside of Europe until 1884. Prior to this, Germany focused on securing an empire within Europe and developing a system of alliances to isolate France. The German Chancellor, Otto Von Bismarck, finally supported the development of an empire also provide Germany with the opportunity to build a new navy and become a world power. Germany’s colonies were in Western Pacific and Africa: it also sought to obtain influence in the Middle East.
WWI was a war between empires because its roots were in Nationalism and Imperialism.
Tensions between countries with colonies increase as they tried to extort influence their own colonies or in the colonies of other colonial powers, increasing the possibility of war.