nail one's colours to the mast

Meaning

Verb

• 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.

Origin

• 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.