Complex sentence: After reclaiming New Granada, Morillo had to go back to Venezuela in 1817 because he was worried about the new outbreak of the war, since Bolívar, Piar, Páez, and other Venezuelan chiefs revived the movements while Morillo was in New Granada.
Split into simpler sentences: After reclaiming New Granada, Morillo has to go back to Venezuela in 1817 because he was worried about the new outbreak of the war, since Bolívar, Piar. Páez and other Venezuelan chiefs revived them movements while Morillo was in New Granada.