Reasons for expansion of World War 1 to Asia Africa and the pacific?

World War I expanded to Asia, Africa, and the Pacific for several reasons. For one, the countries involved in World War 1 has colonies in Asia and Africa. This included Tanganyika, which was under German rule. In addition to German East Africa, the British governed Hong Kong, which was physically located within China. To protect their respective colonies, the nations involved had no choice but to bring the war to these areas.