One of these is a letter (June 2, 1637) from the celebrated martyr in the Japanese missions, Marcelo Francisco Mastrilli, who went to Mindanao with Corcuera. He relates with much detail the events of the expedition, which the devil strives from the start to hinder. The Spaniards capture the Moro forts at the mouth of the Rio Grande, killing several of Corralat's best officers, and seizing many vessels and military supplies; then they destroy many villages belonging to him. On March 18, the Spaniards storm a fortified height back of the port where they first entered. Corralat is driven from it, and flees to a little village in his territory; and in the conflict his wife and many of his followers are slain. Some Recollect fathers, held captive by the Moros, also perish--one of them slain by them, in anger at their defeat. Corralat's treasure is seized, and divided among the soldiers; and much booty obtained by the Moros in plundering the churches in their raids is recovered. After destroying all that can be found, Corcuera returns to Zamboanga, leaving troops behind to subdue another Moro ruler, named Moncay. The wounded Spaniards--many of whom were injured by poisoned arrows--are cared for at Zamboanga, so successfully that only two men out of eighty die, and these "because they would not let themselves be cured." Mastrilli ascribes this success not so much to the antidotes that had been furnished from Manila as to the virtues of a relic that he had, of St. Francis Xavier, and to the patients' faith therein. In due time, the detachment sent against Moncay return, bringing that chief's brother as envoy to offer his submission, and a promise to aid the Spaniards against Corralat, and to receive among his people Jesuit missionaries. Corcuera returns to Manila, after sending an expedition to reduce the villages on the western coast of the island, and arranging for opening a mission on the island of Basilan and securing for its people (who desire to maintain friendship with the Spaniards) the protection of the Spanish fort at Zamboanga. Other Moros along the southern coast offer to become the vassals of Spain, and the Joloans hasten to secure peace with the conqueror. All this opens a broad field for gospel work, and Mastrilli urges that Jesuit missionaries hasten to till it.