thin blue line

noun

: the police imagined as a defensive border or boundary

… the thin blue line that protects us from barbarism and mob rule.

—Theodore Dalrymple

Their image is part of a great American tradition which reflects the constabulary as knights in black and white cruisers, a thin blue line between anarchy and civilization.

—Vernon Scott

… a Columbus police officer and national president of the Fraternal Order of Police, told the committee that only a "thin blue line" separates the "tidal wave" of criminal activity from society.

—David Kelly

—sometimes used before another noun

wore a thin blue line patch/symbol

In Connecticut and around the nation, citizens, public officials, and police have widely varied views on what exactly the "thin blue line" flag stands for. Many see it as a symbol of honor and sacrifice, while others go so far as to call it hateful.

—Jesse Leavenworth

Word History

Etymology

blue representing the traditional color of American police uniforms; after thin red line, a phrase used to describe a line of British infantry soldiers (whose uniforms were in part red) facing a cavalry charge during the Crimean War

Note: The original phrase was "thin red streak tipped with a line of steel," used by The Times correspondent W.H. Russell to describe the Sutherland Highlanders during the battle of Balaclava on October 25, 1854. Subsequently, "thin red line" was used by other reporters, and by Russell himself in a recasting of the line in his book The British Expedition to the Crimea (London, 1877), p. 156.

First Known Use

1945, in the meaning defined above