The Third International was a vast school or parliament where ideas were thrashed out and a common position agreed.
The first four congresses were a milestone. After that, with the defeat of the German Revolution in 1923 and the death of Lenin in 1924, the Russian Revolution was left isolated. In conditions of economic backwardness, this led to the rise of Stalinism.
The adoption of the theory of ‘Socialism in One Country’ resulted in a reformist and nationalist degeneration of the Third International. From being the vanguard of the world revolution, the International was, under Stalin and his cronies, purged of its best elements and turned into a tool of Stalinist foreign policy.
This led to one disaster after another: in China, Germany, Spain, and elsewhere. Eventually in 1943, in a gesture to the Allies, Stalin formally dissolved the Communist International.