Complex sentence: It was supposed to be erected in Petrograd after the Bolshevik Revolution of 1917, as the headquarters and monument of the Comintern-its proper name was to be "The Monument to the Third International".
Split into simpler sentences: It was supposed to be erected in Petrograd after the Bolshevik Revolution of 1917, as the headquarters and monument of the Comintern. Its proper name was to be "The Monument to the Third International".