On a routine cruise to "show the flag," the British warships Amphion and Contest steamed into the harbor of Santa Ana Island in the southern Solomons (which are under a British protectorate).
(idiomatic,by extension) To represent one's country or some other group in a manner intended to suggest the authority or importance of that country or group.
The Bush-Cheney re-election campaign will send a high-profile team of surrogates to both Iowa and New Hampshire in the coming days to train and motivate Republican activists and to "show the flag" in states in which the Democratic presidential race has dominated political debate.