The USS Charleston was given two days to capture the island of Guam, which was under the control of the Spanish at the time. When they arrived to the island, they fired 13 shots at the island and eagerly waited for a response.
They were soon met by a single Spanish officer in a small boat! The officer welcomed the Americans to the island of Guam, thanked them for their 13 shot salute, and then proceeded to apologize that they could not return the salute because they were out of gunpowder!
The war had just begun, and the island of Guam hadn't gotten the message that they were at war with the Americans! They never stocked up on gunpowder because they didn’t think that they needed to. And that is how, without firing a single shot, Guam surrendered to America.