how about 'Standard-bearer'?

> A standard-bearer is a person (soldier or civilian) who bears an emblem called an ensign or standard, i.e. either a type of flag or an inflexible but mobile image, which is used (and often honoured) as a formal, visual symbol of a state, prince, military unit, etc. ([Wikipedia][1])


Here's some reference to suggest the importance of a Standard bearer in battle.

> The Standard Bearer should never surrender his Banner, if he, during a battle, could no longer safeguard the Banner; he should wrap his body into the Banner awaiting the final slash. ([Safeguarding the flag][2])


  [1]: https://en.wikipedia.org/wiki/Standard-bearer
  [2]: http://www.navalhistory.dk/English/TheFlag/The_Standard_Bearer.htm