Quotation from: The Gods of Mars

Written by: Edgar Rice Burroughs

There were two men and four females in the party and their ornaments
denoted them as members of different hordes, a fact which tended
to puzzle me infinitely, since the various hordes of green men of
Barsoom are eternally at deadly war with one another, and never,
except on that single historic instance when the great Tars Tarkas
of Thark gathered a hundred and fifty thousand green warriors from
several hordes to march upon the doomed city of Zodanga to rescue
Dejah Thoris, Princess of Helium, from the clutches of Than Kosis,
had I seen green Martians of different hordes associated in other
than mortal combat.