The Presidency of the Council of Ministers grew as an executive superstructure with the beginning of the "Estado Novo" regime, especially after the Constitution of 1933 came into force, as a mechanism to centralise political power and reinforce government authority. The 1950s and 1960s saw a growing government bureaucracy to overcome the new challenges in economic policy, public safety and national defence, in the context of the post-war international situation, of Portugal's NATO membership, and of the Colonal War.