Complex sentence: In 1912, Matienzo Cintrón became convinced the party was not doing enough to promote Puerto Rico's independence and left the party in order to organize a new party, the "Partido de la Independencia".
Split into simpler sentences: In 1912, Matienzo Cintrón became convinced the party was not doing enough to promote Puerto Rico's independence. He left to organize another party, the "Partido de la Independencia".