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 September 17, 1957, ending Phibun's career for good. 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.