Wiktionary
vb. 1 (context literally English) To display the flag of one's country, especially as an expression of patriotic pride. 2 (context idiomatic English) Of a naval vessel or military force, to identify itself by displaying the flag of its country of origin, especially in order to establish an authoritative presence and to exert diplomatic or political influence. 3 (context idiomatic by extension English) To represent one's country or some other group in a manner intended to suggest the authority or importance of that country or group.
Usage examples of "show the flag".
Augustine, show the flag in Georgia and the Carolinas, and sail either for the West African coast or to Barbados to capture British slave ships bound for the West Indies.
He should come over, briefly, show the flag -- they think he's God, you know.
I knew, as all the world did, that Grant was due in Hong Kong shortly with a fleet and army whose purpose would be to go up-country and force our latest treaty down the Chinese Emperor's throat, but it wasn't liable to be much of a war: show the flag to the Chinks, kick a few yellow backsides, and home again with hardly a shot fired - the kind of campaign that would have suited me, if I'd been looking for one, which I wasn't.
Have to show the flag, go out on these inspection tours, give the frontline troops a glimpse of glory, build morale.
We'll have more revolts if we do no show the flag in the distant provinces.
Somehow the Survey Service never seems to show the flag in that sector of space.
Do you think I should take a swing around the state in the spring, show the flag?
What they came up with was this: several state troopers and Blue Kills policemen took a coast guard boat out to the Blowfish-which a trooper boarded, just to show the flag-and then their boat escorted us way around to the north and into a dock that was part of Blue Kills proper, not Blue Kills Beach.