High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! Red flags can signify a warning, martial law, defiance, or left-wing politics. The earliest citation for "red flag" in the Oxford English Dictionary is from 1602 and shows that at that time the flag was used by military forces to indicate that they were preparing for battle. It has been associated with left-wing politics since the French Revolution. Socialists adopted the symbol during the Revolutions of 1848 and it became a symbol of communism as a result of its use by the Paris Commune of 1871. The flags of several communist states, including China, Vietnam, and the Soviet Union, have red backgrounds. The Labour Party in Britain used it until the late 1980s, and the French Socialist Party uses it. The earliest citation of "red flag" in the sense of a warning is dated 1777 and refers to a flag warning of flood.