The International Code flags and pennants enable mariners to communicate regardless of differences of language. In the armies and navies of the various nations of the world, flags are used for signaling. The white flag is used universally for truce; the black in early times was a symbol for piracy; the red symbolizes mutiny or revolution; the yellow is a sign of infectious diseases. Shipping lines have their own flags. Striking a flag signifies surrender, and the flag of a victor is hoisted above that of the vanquished. A flag flown at half-mast is the symbol of mourning. The inverted national ensign is a signal of distress.
