Use in the Real world
The Bronze Star is a famous award currently being given out in the United States to soldiers that preform "Heroic or meritorious achievement or service." It came about by Executive Order 9419.
Empire Use in Runescape
Due to the fact that in Runescape, it's impossible to die and stay dead, so any amount of self sacrifice is hard to measure, so it's left up to Legion Commanding Officers to determine who is awarded this award, which can be overturned by the Inner Circle.
" Recipients shall have demonstrated Heroic or meritorious achievement or service while on the battlefield in the name of The Empire."