A mass anticommunist and antiparliamentary Vaps Movement emerged in the 1930s. In October 1933 a referendum on constitutional reform initiated by the Vaps Movement was approved by 72.7 percent. The league spearheaded replacement of the parliamentary system with a presidential form of government and laid the groundwork for an April 1934 presidential election, which it expected to win. However, the Vaps Movement was thwarted by a pre-emptive coup d'état on 12 March 1934, by Head of State Konstantin Päts, who then established his own authoritarian rule until a new constitution came to force. During the Era of Silence, political parties were banned, and the parliament was not in session between 1934 and 1938 as the country was ruled by decree by Päts. The Vaps Movement was officially banned and finally disbanded in December 1935. On 6 May 1936, 150 members of the league went on trial and 143 of them were convicted to long-term prison sentences. They were granted an amnesty and freed in 1938, by which time the league had lost most of its popular support.