Complex sentence: After the destruction of Portobelo in November last year, Vernon proceeded to remove the last Spanish stronghold in the area, attacking the fortress of San Lorenzo el Real Chagres, on the banks of the Chagres River and near Portobelo.
Split into simpler sentences: After the destruction of Portobelo the previous November, Vernon proceeded to remove the last Spanish stronghold in the area. He attacked the fortress of San Lorenzo el Real Chagres, on the banks of the Chagres River, near Portobelo.