Private signals between the U.S. and British navies, by day and night
During the Quasi-War with France, United States Navy ships had their own set of signals for identifying each other [see 2506.1, Box 1, Folder 11], but this separate set of coded signals allowed U.S. and British ships to identify each other. Sailing ships could look very similar at a distance, and it was critical for them to identify each other as soon possible to avoid friendly fire. At the same time, ships often sought to deceive the enemy about their identity. Complex signal arrangements like these were intended to provide clear identification while making it impossible for an enemy to announce themselves as a friendly vessel.