by the pro-government air force. New constitution in 1949 In 1949 a new constitution was promulgated, creating a senate appointed by the king (in practice, by the government). But in 1951 the regime abolished its own constitution and reverted to the 1932 arrangements, effectively abolishing the national assembly as an elected body. This provoked strong opposition from the universities and the press and led to a further round of trials and repression. The regime was greatly helped, however, by a postwar boom which gathered pace through the 1950s, fuelled by rice exports and US aid. Thailand's economy began to diversify, while the population and urbanisation increased. Power play In 1956, it became clearer that Plaek, allied to Phao, was losing to another influential groups led by Sarit, and consisted of "Sakdina" (royalties and royalists). Both Plaek and Phao intended to bring home Pridi Banomyong to clear his name from the mystery around the death of King Rama VIII. However, the US government disapproved, cancelling the plan. In June 1957, he told one of Pridi's son to "tell your father that I want [him] to come back [and] help me work for the nation. I alone can no longer contest Sakdina." Sarit Dictatorship and the Restoration of Monarchy (1957–1963) By 1955, Phibun was losing his leading position in the army to younger rivals, led by Field Marshal Sarit Thanarat and General Thanom Kittikachorn. To shore up his position he restored the 1949 constitution and called elections, which his supporters won. But the army was not prepared to give up power, and in September 1957 it demanded Phibun's resignation. When Phibun tried to have Sarit arrested, the army staged a bloodless coup on 17 September 1957, ending Phibun's career for good. Sarit began the restoration of the monarchy so much that by Thanom's time their rule was a close partnership between the military and the king. In this period the Monarchy was again restored its power since the Siamese revolution in 1932. Cold War and pro-American period (1963–1973) Thanom became prime minister until 1958, then yielded his place to Sarit, the real head of the regime. Sarit held power until his death in 1963, when Thanom again took the lead. Sarit and Thanom were the first Thai leaders to have been educated entirely in Thailand, and were less influenced by European political ideas, whether fascist or democratic, than the generation of Pridi