After the armistice of November 11, 1918 and the 1919 Peace Conference, German East Africa was turned over to the British and became known as Tanganyika. Horace Byatt had been in charge of German East Africa since 1917, and on January 31, 1919 he became Civil Administrator. In 1919 the Indians refused to vote for two members of the Legislative Council because many fewer Europeans were allowed to elect eleven. The League of Nations came into existence in January 1920, but the B mandates did not take effect until July 1922. The Administrator Byatt became the Governor and Commander-in-Chief. In 1920 the judiciary was revised by the Courts Ordinance, and the departments of Agriculture, Forest, Education, and Land Survey were created. Between 1920 and 1922 the British provided Tanganyika with £408,000 in grants-in-aid, and Governor Byatt tried to increase revenue by promoting African cash crops. On March 22, 1921 the Belgians ceded Ujiji District and the parts of Ufipa and Biharamulo they had held. The Belgian mandate of Rwanda-Urundi was fixed in December 1923.
In 1922 Martin Kayamba and other educated Africans formed the Tanganyika Territory African Civil Servants Association. They started libraries and bought newspapers. Education lagged behind what the Germans had, and in 1924 Tanganyika had only 72 schools in rural areas. Conflict in the Chagga and Haya regions led coffee growers to form associations to compete with the chiefs, who were educated and became a privileged group. In 1924 other educated Haya organized the Bukoba Buhaya Union and demanded equal opportunity in education and a share of coffee profits. Major C. St. J. Orde Browne was appointed Special Labour Commissioner to investigate labor problems. The Phelps-Stokes Commission visited in 1924, and the Government encouraged mission schools; but in 1925 Africans were not allowed to be in the same schools as Indians lest they get political ideas. A school in Tabora was restricted to the sons of chiefs and headmen.
Governor Donald Cameron (1925-31) did not approve an Advisory Council. In 1925 the Chagga asked the Governor to let them export coffee through the Kilimanjaro Native Planters' Association because Indian merchants had combined to keep their prices down. In 1926 the Masters and Servants Ordinance required paying wages in cash and reporting any serious injury to an employee. The first Legislative Council met on December 7, 1926 with fourteen officials and five Europeans and two Indians as unofficials. In 1927 Cameron opposed the federation plan of the Hilton Young Commission; but Tanganyika adopted the customs tariff used in Kenya and Uganda, and the three territories agreed to free trade across their borders. The African Education Ordinance provided for grants-in-aid to begin January 1, 1928, and the Government's budget for education increased to £80,000 a year. This was less than the Medical Department, which the East Africa Commission considered just as understaffed as the Education and Agricultural departments.
In 1929 the Native Courts Ordinance removed the supervision of the High Court from the native courts and placed them under the Provincial Administration. The African chiefs were authorized to maintain order and collect taxes, and they could use a portion of the taxes and fines for administration. That year Tanganyika began grants-in-aid to Indian schools. The unofficial members of the Legislative Council were increased, but still no Africans were appointed. Cameron reorganized the 22 districts into eleven provinces. He appointed Charles Dundas as secretary for native affairs, and he was succeeded by Philip Mitchell. Governor Cameron opened up the Iringa area and other places for settlement, and he allowed Germans to return. In 1929 the Tanganyika African Association (TAA) was formed as a national improvement organization, and they formed nine branches. In 1930 the Tanganyika Sisal Growers' Association was formed to try to reduce wages.
The depression of the early 1930s caused Tanganyika's major exports of sisal and coffee to fall sharply. Sisal had been selling for £32 a ton, but by 1931 the price was only £12 a ton. In 1931 Tanganyika had 8,200 Europeans but 25,000 Indians. That year a Parliament committee in London listened to influential Africans object to enlarging the political power of white settlers. Governor Stewart Symes (1931-34) tried to increase agricultural production, especially by Africans. Prices began to rise in 1933, and in 1935 the sisal exported was worth £1,000,000. Cotton revived, and tea and sugar were successfully produced. In 1936 the Bukoba Buhaya Union protested the chiefs' new coffee rules. When riots resulted, the British jailed the leaders. Erica Fiah founded the Tanganyika African Welfare and Commercial Association, and in 1937 he founded the Swahili newspaper, Kwetu.
By the end of the 1930s gold had become a major export. In 1938 the Governor agreed to contribute £100,000 to Makerere College in Uganda to train professionals. After World War II began in September 1939, Tanganyika exhausted its reserves by giving £200,000 to Britain. Because the territory had 3,205 Germans compared to 4,054 British residents, the enemy aliens were interned during the war. German leaders, confident of victory, instructed the settlers not to resist. About 87,000 Africans in Tanganyika were conscripted for service in the war. In 1940 all incomes over £350 a year were taxed, and the next year all those over £200 were taxed.
During the first five years after World War II Tanganyika developed its economy, and their trade tripled in three years. The TAA continued to agitate for more opportunities for Africans. Two Africans were appointed to the Legislative Council in 1945, and two more were added in 1948; but the Europeans had seven unofficial members and the Asians three. At a conference at Dar es Salaam in 1946 they called for the election of Africans to representative councils and self-government. The United Nations Trusteeship Council urged Britain to develop Tanganyika toward independence, and its first mission visited the colony in 1948. When Edward Twinning became governor in 1949, he appointed a committee to investigate constitutional development.