Be polite, be professional, but have a plan to kill everybody you meet.
One of the rules Maj. Gen. James Mattis gave his Marines to live by in Iraq, as quoted in Fiasco: The American Military Adventure in Iraq (2006) by Thomas E. Ricks; as excerpted in Armed Forces Journal (August 2006)
None of the widely touted new technologies and weapons systems "would have helped me in the last three years [in Iraq and Afghanistan]. But I could have used cultural training [and] language training. I could have used more products from American universities [who] understood the world does not revolve around America and [who] embrace coalitions and allies for all of the strengths that they bring us."James Mattis
In this age, I don’t care how tactically or operationally brilliant you are, if you cannot create harmony even vicious harmony on the battlefield based on trust across service lines, across coalition and national lines, and across civilian/military lines, you need to go home, because your leadership is obsolete. We have got to have officers who can create harmony across all those lines.James Mattis
PowerPoint makes us stupid.James Mattis
Treachery has existed as long as there’s been warfare, and there’s always been a few people that you couldn’t trust.James Mattis