What is the story behind the phrase "raise a flag"?

closed as general reference by FumbleFingers, Alenanno, Hugo, Mehper C. Palavuzlar, TimLymington Jan 16 '12 at 15:24

This question is too basic; it can be definitively and permanently answered by a single link to a standard internet reference source designed specifically to find that type of information. If this question can be reworded to fit the rules in the help center, please edit the question.

  • There's also raise the flag which is four times more common. The "story" behind both usages is trivial. Voting to close as "general reference" – FumbleFingers Jan 16 '12 at 12:37
  • If you find the story behind either usage trivial and can back that up with sources, then go ahead and answer the question. – Illotus Jan 16 '12 at 14:09
  • There were already three answers, and I don't see I could have added much anyway. Apart from pointing out that in this modern computing age it's also more common to actually set(a) flag. But any dictionary will give these usages, and frankly there isn't much of a "story" behind any of them. – FumbleFingers Jan 16 '12 at 15:03

There are so many situations where a physical flag is raised to draw attention to a problem or situation, that it's probably not possible to narrow down which one is responsible for the idiom.

  • In sports, the linesman raises a flag when a foul is committed (to draw the referee's attention)
  • A ship raises a particular kind of flag to signal distress etc.
  • Before radio technology, flags would have been used extensively as signals in military operations
  • Flags are still used in traffic control

Note also that "flag", as well as meaning as piece of cloth designed for display, also means anything used to draw attention.


raise a flag as an idiom seems to be present at least since the mid 19C in a sense similar to what it is used for in programming today.

ABA Jnl. Sep.1955 [v.41 p.819]
Publishers of legal services should annotate or cite applicable treaties which affect statutory law, or raise a flag in the preface that no consideration is given to treaty-made law.
(emphasis mine.)

This reference suggests that to 'raise a flag' means to 'call attention to ...' or 'announce prominently'.


Raise a flag means "bring something to notice". The phrase Raise a flag is originated from "raise a red flag" which means to alert someone about a potential danger or trouble ahead, the origin being that red flags are often literally used to warn people of possible peril.

Raise a flag has different meanings in different contexts.For example:- In Sports Raising a flag indicates an offside offence. And in the context of war Raise flag means Declaration of war. Also see Raising the first flag

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