The CPSU was a communist party organized on the basis of democratic centralism, a principle conceived by Lenin that entails democratic and open discussion of policy issues within the party followed by the requirement of total unity in upholding the agreed policies. The highest body within the CPSU was the party Congress, which convened every five years. When the Congress was not in session, the Central Committee was the highest body. Because the Central Committee met twice a year, most day-to-day duties and responsibilities were vested in the Politburo, the Secretariat, and the Orgburo (until 1952). The party leader was the head of government and held the office of either General Secretary, Premier or head of state, or some of the three offices concurrently—but never all three at the same time. The party leader was the de facto chairman of the CPSU Politburo and chief executive of the USSR; the tension between the party and the state (Council of Ministers of the Soviet Union) for the shifting locus of power was never formally resolved, but in reality the party dominated, and a paramount leader always existed (first Lenin and thereafter the General Secretary).