World War I had only a minimal military impact on Sri Lanka, which entered the war as part of the British Empire. The closest fighting took place in the Bay of Bengal, where an Australian warship sank a German cruiser. But the war had an important influence on the growth of nationalism. The Allies' wartime propaganda extolled the virtues of freedom and self-determination of nations, and the message was heard and duly noted by Sri Lankan nationalists. There was, however, an event, only indirectly related to the war, that served as the immediate spark for the growth of nationalism. In 1915 communal rioting broke out between the Sinhalese and Muslims on the west coast. The British panicked, misconstruing the disturbances as part of an antigovernment conspiracy they blamed the majority ethnic group and indiscriminately arrested many Sinhalese, including D.S. Senanayake--the future first prime minister of Sri Lanka--who had actually tried to use his influence to curb the riots. The British put down the unrest with excessive zeal and brutality, which shocked British and Sri Lankan observers alike. Some sympathetic accounts of the unrest take into consideration that the judgment of the governor of the time, Sir Robert Chalmers (1913-16), may have been clouded by the loss of his two sons on the Western Front in Europe. At any rate, his actions insured that 1915 was a turning point in the nationalist movement. From then on, activists mobilized for coordinated action against the British.

The nationalist movement in India served as a model to nationalists in Sri Lanka. In 1917 the Indian National Congress and the Muslim League mended their differences and issued a joint declaration for the "progressive realization" of responsible government in India. Nationalists in Sri Lanka learned from their Indian counterparts that they had to become more national and less partisan in their push for constitutional reform. In 1919 the major Sinhalese and Tamil political organizations united to form the Ceylon National Congress. One of the first actions of the congress was to submit a proposal for a new constitution that would increase local control over the Executive Council and the budget. These demands were not met, but they led to the promulgation of a new constitution in 1920. Amendments to the constitution in 1924 increased Sri Lankan representation. Although the nationalists' demand for representation in the Executive Council was not granted, the Legislative Council was expanded to include a majority of elected Sri Lankan unofficial members, bringing the island closer to representative government. Yet the franchise remained restrictive and included only about 4 percent of the island's population.

Data as of October 1988