“Be polite, be professional, but have a plan to kill everybody you meet.”
Before his Marines deployed to Iraq in 2003, he told them this (along with many other great pieces of advice in a now-famous letter). His point here is to be a professional warfighter who can be polite with civilians, but always remember that if things go south, the dirty work needs to get done.
Full article here
Full letter to his Marines here
Update: Just ran across this Mattis
"Yes...I know" this is not an article about Treasure Hunting, but being a Marine myself, I love all things Marine Corps. I suspect more post about the Marine Corp and the great leaders it produces...