Authors:

A warrior may change his metal, but not his heart.

Edgar Rice Burroughs (2015). “A Princess of Mars (Science Fiction Classic): From the Author of Tarzan of the Apes, Barsoom Series, Llana of Gathol, Pirates of Venus, The Land That Time Forgot & Pellucidar”, p.62, e-artnow
A warrior may change his metal, but not his heart.