Complex sentence: That Brazil meant to absorb Uruguay (said the Paraguayan government) was a known fact, because for Brazil it was a matter of sheer necessity: most of Brazil lay in the "Torrid Zone"-- "only habitable by Africans".
Split into simpler sentences: That Brazil meant to absorb Uruguay (said the Paraguayan government) was a known fact, because for Brazil it was a matter of sheer necessity. It was a matter of necessity because most of Brazil lay in the "Torrid Zone"-- "only habitable by Africans".