“ Charleston fired upon the island from three of its cannons. The barrage apparently did no harm, since a ship flying the Spanish flag soon appeared, and the Spanish officer climbed aboard Charleston and asked to borrow some powder from the Americans to return their salute. Glass informed the officer that war had been declared between the two nations and that the officer was a prisoner of war. He then paroled the officer and sent him back to the island with the message to surrender the island.”
Capture of Guam - Wikipedia, the free encyclopedia
Apparently this is why we now have Guam.