nail one's colours to the mast

• pin one's colours to the mast

From the naval military practice of displaying one's colours (signal flags or insignia) from the mast of a ship during battle to show loyalty. To surrender, one would strike one's colours, i.e. take down one's flag. If a ship nailed its colours to the mast, it would fight to the death and not surrender.

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nail one's colours to the mast (third-person singular simple present nails one's colours to the mast, present participle nailing one's colours to the mast, simple past and past participle nailed one's colours to the mast)

1. To clearly show one's support for a side or opinion in a dispute, often indicating an intention to defend that side to the end.
   • 1808, Sir Walter Scott, Marmion, Canto I, Introduction, Stanza 10:

     Stood for his country’s glory fast,
     And nail’d her colours to the mast!

   • 2017 June 9, Steven Poole, “Behave by Robert Sapolsky review – why do we do what we do?”, in The Guardian‎, →ISSN:

     He eventually nails his colours to the mast of strict determinism: every human action is inescapably caused by preceding events in the world, including events in the brain.

• raise the flag and see who salutes
• show one's true colors
• stand up and be counted