The rank and title of Master Sergeant is a senior non-commissioned officer's rank used mostly by army organizations. They are highly regarded as both experts in their particular field and natural leaders.
In New Republic Service Edit
Master Sergeants in the New Republic Army hold the same pay grade as a First Sergeant, but is given a very different responsibility. With at least twelve years time in service (usually pushing fifteen), Master Sergeants do not carry all the responsibilities of their First Sergeants.