Merriam-Webster’s Dictionary of Allusions:
IN HARM’S WAY In a dangerous place or situation. Particularly applied to the members of the armed services in a war or threat of war.
The phrase comes from America’s Revolutionary War naval hero, John Paul Jones. In a letter dated November 16, 1778, he wrote, “I wish to have no connection with any ship that does not sail ‘fast’; for I intend to go ‘in harms way.’” He was in France at the time seeking a ship; the French offered him several, prizes taken from the British. He finally took the ship he named ‘Bonhomme Richard.’
Ken Greenwald (Fort Collins, Colorado – U.S.A.)