 The British firm of Lever Bros. greatly expanded the palm oil business during the war, and output of cocoa, rice and cotton increased.New rail and steamship lines opened to handle the expanded export traffic.During the First World War (1914–1918), the system of "mandatory cultivation" ("cultures obligatoires") was introduced, forcing Congolese peasants to grow certain cash crops (cotton, coffee, groundnuts) destined as commodities for export.