Under the care of Benavides and Cobo the mission flourished, and the two fathers became increasingly proficient in the Chinese language. When the provincial Juan de Castro began making preparations for an inspection tour of his Chinese vicariate in 1590, he chose as his companion Miguel de Benavides. The account of the events leading up to this expedition is given in the already quoted letter of Salazar on the Chinese: "Of the Dominican religious who came to these islands, four are engaged in ministering to the Sangleys. Two of these four officiate in the Church of San Gabriel, which, together with the house where the religious live, stands close to the Parian. Another church with its house is on the promontory of Baybay, near Tondo--which a river divides, separating it from Manila. Two of the four have learned the language of the Sangleys so well, and one of these two how to write also (which is the most difficult part of the language), that the Sangleys wonder at their knowledge.... After due consideration of the matter, the Dominican fathers and myself decided that it was necessary to go to China.... Thus we decided upon the departure, sending at present no more than two religious: Fray Miguel de Benavides, who was the first to learn the language of the Sangleys; and Father Juan de Castro, who came as vicar of the religious and who was made provincial here. We preferred these two, as one is well acquainted with the language, and the other is much loved and esteemed by the Sangleys on account of his venerable gray locks and blessed old age; and we know that in that land old people are much respected and revered." [108] They sailed on May 22, 1590, but Juan de Castro before he left appointed Cobo acting superior of the province with full authority during his absence, and in the latter's place as head of the Chinese mission sent Juan de San Pedro Martyr.