Spanish naval ship San Quintín
The year was 1885 and tension between Spain and Germany had already been at the boiling point for about a year.
Both countries were claiming control over the Caroline Islands (Palau, Yap, Chuuk, Ponape, Kosrae). Spain asserted that these islands had been Spanish since the old days of discovery. Germany countered, saying that Spain had ignored them for all those hundreds of years and were therefore "up for grabs."
The conflict was headed for military resolution and Spain began her preparations. Spanish naval ships had to head for Yap, the focus of the controversy.
It seems that Chamorro men were part of the preparations.
Francisco Olive García, the Spanish Governor of the Marianas, relates in his 1887 book on the Marianas (Islas Marianas : Lijeros Apuntes), that he heard good things about the Chamorros who were "volunteers to serve on our war ships in the year 1884."
He might be referring to any one of three Spanish ships that went to Yap in 1885. The Velasco came in February. But that ship was not a war ship and its purpose was to gather information about the island, and then leave.
In August, however, two military ships, the San Quintín and the Carriedo (also known as the Manila), arrived at Yap with the intention of establishing a Spanish presence there. Two Spanish priests came to build a church there. One of these two priests, Father Aniceto Ibáñez, had previously been the priest of Hagåtña for many years, and was embraced at Yap by some Chamorros who had moved there. Knowing he would be going to an island where some Chamorros already lived, it's plausible that Ibáñez suggested (or at least concurred) that some Chamorro volunteers be part of the expedition to Yap.
I would not be surprised, therefore, if our Chamorro volunteers assisting the Spanish cause in Yap had been on the same ship that brought Ibáñez to Yap, the San Quintín.
In any case, they didn't stay long. The Germans arrived a few days later with their own war ship and the Spaniards departed Yap.
I haven't found any other details about these Chamorro volunteers. How many were there? Did they indeed go to Yap? From Guam or from Manila? How many were they? What were their names? Where did they go when all was done?
All I know, from Olive's remark, is that there were Chamorro volunteers on ships in the service of Spain in 1884.