In the 1950s, Los Angeles Police Chief Bill Parker often used the term in speeches, and he also lent the phrase to the department-produced television show The Thin Blue Line.

New York police commissioner Richard Enright used the phrase in 1922. It is unknown when the term was first used to refer to police. In the poem, the phrase is used to refer to the United States Army, alluding both to the Thin Red Line and to the fact that US Army soldiers wore blue uniforms from the eighteenth century through the nineteenth century. Īn early known use of the phrase 'thin blue line' is from a 1911 poem by Nels Dickmann Anderson, titled 'The Thin Blue Line'. In the book Lawtalk, James Clapp and Elizabeth Thornburg say the term spread to other professions, e.g., a 'thin white line of bishops'. The name is now used for firefighters today. This action was widely publicized by the press and recreated in artwork, becoming one of the most famous battles of the Crimean War. The term is derived from the Thin Red Line, a formation of the 93rd Highland Regiment of Foot of the British Army at the Battle of Balaclava in 1854, in which the Scottish Highlanders stood their ground against a Russian cavalry charge. The 'thin blue line' has also been associated with white nationalists in the US, particularly after the Unite the Right rally in 2017. The 'thin blue line' has been appropriated by the ' Blue Lives Matter' movement, which began December 2014, after the homicides of NYPD officers Rafael Ramos and Wenjian Liu in Brooklyn, New York, in the wake of the homicides of Eric Garner and Michael Brown Jr earlier that year and in the context of the greater Black Lives Matter movement. Its use referring specifically to the police was popularized by Los Angeles Police Chief Bill Parker during the 1950s author and police officer Joseph Wambaugh in the 1970s, by which time 'thin blue line' was used across the United States and Errol Morris's documentary The Thin Blue Line (1988). The phrase originated as an allusion to the British infantry regiment The Thin Red Line during the Crimean War in 1854, wherein the regiment of Scottish Highlanders-wearing red uniforms-famously held off a Russian cavalry charge. The 'blue' in 'thin blue line' refers to the blue color of the uniforms of many police departments. The ' thin blue line' is a term that typically refers to the concept of the police as the line which keeps society from descending into violent chaos.

Blue and black flag