<P> Estimates of the total death toll vary considerably . As the first census did not take place until 1924, it is difficult to quantify the population loss of the period . Casement's report set it at three million . William Rubinstein wrote: "More basically, it appears almost certain that the population figures given by Hochschild are inaccurate . There is, of course, no way of ascertaining the population of the Congo before the twentieth century, and estimates like 20 million are purely guesses . Most of the interior of the Congo was literally unexplored if not inaccessible ." See Congo Free State for further details including numbers of victims . </P> <P> A similar situation occurred in the neighbouring French Congo . Most of the resource extraction was run by concession companies, whose brutal methods, along with the introduction of disease, resulted in the loss of up to 50 percent of the indigenous population . The French government appointed a commission, headed by de Brazza, in 1905 to investigate the rumoured abuses in the colony . However, de Brazza died on the return trip, and his "searingly critical" report was neither acted upon nor released to the public . In the 1920s, about 20,000 forced laborers died building a railroad through the French territory . </P> <P> French diplomat Ferdinand de Lesseps had obtained many concessions from Isma'il Pasha, the Khedive of Egypt and Sudan, in 1854--56, to build the Suez Canal . Some sources estimate the workforce at 30,000, but others estimate that 120,000 workers died over the ten years of construction due to malnutrition, fatigue and disease, especially cholera . Shortly before its completion in 1869, Khedive Isma'il borrowed enormous sums from British and French bankers at high rates of interest . By 1875, he was facing financial difficulties and was forced to sell his block of shares in the Suez Canal . The shares were snapped up by Britain, under its Prime Minister, Benjamin Disraeli, who sought to give his country practical control in the management of this strategic waterway . When Isma'il repudiated Egypt's foreign debt in 1879, Britain and France seized joint financial control over the country, forcing the Egyptian ruler to abdicate, and installing his eldest son Tewfik Pasha in his place . The Egyptian and Sudanese ruling classes did not relish foreign intervention . </P> <P> During the 1870s, European initiatives against the slave trade caused an economic crisis in northern Sudan, precipitating the rise of Mahdist forces . In 1881, the Mahdist revolt erupted in Sudan under Muhammad Ahmad, severing Tewfik's authority in Sudan . The same year, Tewfik suffered an even more perilous rebellion by his own Egyptian army in the form of the Urabi Revolt . In 1882, Tewfik appealed for direct British military assistance, commencing Britain's administration of Egypt . A joint British - Egyptian military force ultimately defeated the Mahdist forces in Sudan in 1898 . Thereafter, Britain (rather than Egypt) seized effective control of Sudan . </P>

What were four methods of european colonial control that emerged over time