Promoted to CCS Class II in December 1937, he was attached to the General Treasury and in July 1939 in addition to duties he was appointed deputy director of Civil Aviation and Registrar of Aircraft and Assistant Secretary to the Minister for Communication and Works August 1939.
Mahajana Eksath Peramuna won a landslide victory in the 1956 general elections, defeating the United National Party and paving the way for Bandaranaike to become prime minister.
[10] In this capacity he implemented policies to change the composition of the army to match the demographically ratios of the population, increasing the number of Sinhala Buddhist officers in the armed forces.
[11] In April 1961, Bandaranaike declared a state of emergency in the northern province and ordered the army to clear the Satyagraha organized by the Tamil Federal Party against the Language policy of the government.
In response to this incident and Chelvanayakam's claim that "we resorted to direct action to win our freedom" during the satyagraha, Dias proposed the increase of armed forces deployed to the northern and eastern province and called for the formation of military bases in Arippu, Maricchikatti, Pallai, Thalvapadu, Pooneryn, Karainagar, Palaly, Point Pedro, Elephant Pass, Mullaitivu and Trincomalee to counter possible rise of Tamil separatism.
The case was subsequently dismissed when the jury unanimously acquitted all of the accused in a plot to overthrow the legally elected government due to lack of evidence.