Passage: In 1916 during World War I British and British Indian soldiers won the Tanganyika Territory from the Germans and after the war the British continued to rule the territory, which was a League of Nations mandate from 1922. The continuous line of colonies was complete. The British Empire possessed the political power to complete the Cape to Cairo Railway, but economics, including the Great Depression of the 1930s, prevented its completion before World War II.  After World War II, the decolonisation of Africa and the establishment of independent countries removed the colonial rationale for the project and increased the project's difficulty, effectively ending the project.

Question: Which event halted its progress?
Great Depression of the 1930s