A flag, especially one flown at the bow of a ship to indicate her nationality.
A pirate flag depicting a skull-and-crossbones. It was an invitation to surrender, with the implication that those who surrendered would be treated well. A red flag indicated "no quarter."
Red Ensign (also Red Duster)
A British naval flag.
To lower, specifically a ship’s flag as a signal of surrender.
A yellow flag flown to indicate the presence of an illness, often yellow fever, aboard a ship. Often the flag is used to trick pirates into avoiding potential targets.