During the 1898 war with Spain, then Lieutenant Winslow served on board the gunboat . He was commended for extraordinary heroism when, on May 11, 1898, he commanded a boat expedition from "Nashville" and which succeeded in cutting two submarine cables off Cienfuegos, Cuba, which linked Cuba with Europe. Despite enemy fire from point-blank range, which resulted in a bullet wound to his hand, Winslow retained command throughout the engagement. At that time, regulations did not allow Navy officers to receive the Medal of Honor. However, all the enlisted sailors involved in the cable cutting operation did receive the Medal of Honor.