At the time of the March 1919 uprising which proclaimed a Hungarian Soviet Republic with Béla Kun as "de facto" leader, Pogány cast his lot decisively with the revolution. The Communist Party of Hungary (KMP) first merged with radical members of the Social Democratic Party to form a single organization. Pogány was one of five party leaders signing the unity document on behalf of the Left Socialists. While the two parties were formally ratifying the agreement, Pogány's Soldiers' Soviet assumed control of the Budapest police, occupied the collector jail, and dispatched armed bands throughout the capital to intimidate political opponents.