The First World War was the first fighting happened between the imperialist nations such as Germany, Italy and Austria Hungary (Tripple Alliance) against Britain, France, and Russia (Tripple Entente). This war started from July 1914 and ended on November 1918, it fought on European soil and spread to other parts of the world especially in Africa and Asia where people joined the war to support the colonial masters.

Causes of the First World War
Development of capitalism to the highest stage of imperialism (Monopoly capitalism) so this stage caused competition between the European powers such as Britain, France, Germany, Italy, Belgium, and Portugal to scramble for colonies in order to get their demands such as raw materials, cheap labor, markets, and Areas for investment.
Formation of alliances, this was the development of alliances that were formed by the European nations in order to defend their members militarily once they were attacked by another power. These alliances were Tripple Alliances which was formed by Germany under Bismarck with Austria-Hungary in 1879 and Italy was added in 1882 and Tripple Entente was formed by Britain, France, and Russia in 1907.
German growth as a powerful industrial nation, German manufactured more than European powers including Britain which had been the workshop and manufacturer of the world. So German developed more in finance, shipping, and its population so this situation threatened other countries such as Britain and France so they had to join with others to fight and suppress the growth of German industrial developments.
Effects of First World War in Tanganyika
Tanganyika colony changed hands from the Germans to the British
Death and destruction because Tanganyika was also required to fight in the war to help their colonial masters.
The spread of diseases like small pox, malaria, typhoid and others and all these caused the loss of African lives.
Hunger and famine occurred due to the decline of production, the war caused the decline of agricultural production.
The war caused the intensification of colonial exploitation to cover the cost of the war i.e increasing of taxation, forced labor, and low wages.