Retired Gen. James Mattis earned the nickname "Mad Dog" for leading U.S. Marines into battle in Fallujah, Iraq, in April 2004. In that assault, members of the Marine Corps, under Mattis' command, shot at ambulances and aid workers. They cordoned off the city, preventing civilians from escaping. They posed for trophy photos with the people they killed.
Each of these offenses has put other military commanders and members of the rank and file in front of international war crimes tribunals. The doctrine that landed them there dates back to World War II, when an American military tribunal held Japanese Gen. Tomoyuki Yamashita accountable for war crimes in the Philippines. His execution later was upheld by the U.S. Supreme Court.
During the siege of Fallujah, which I covered as an unembedded journalist, Marines killed so many civilians that the municipal soccer stadium had to be turned into a graveyard.