Complex sentence: Jesús Hernández Tomás, another Communist leader and commissar of the army group in the central-south area, had beaten the rebels, formed a new Politburo and published a manifesto on behalf of the new leadership on 9 March 1939.
Split into simpler sentences: Jesús Hernández Tomás, the Communist commissar of the army group in the central-south area, had beaten the rebels there. He formed a new Politburo and published a manifesto on behalf of the new leadership on 9 March 1939.