nail one's colours to the mast

/N EY1 L W AH0 N EH0 S K AH0 L ER0 Z T UW0 DH AH0 M AE0 S T/
verb
  1. 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.

Source: https://en.wiktionary.org/wiki/nail%20one's%20colours%20to%20the%20mast