A spear or pike thrust aimed backward, or a soldier armed with such a weapon (archaic military term).
Back + spear; from Old English 'spere.' This term appears in medieval military terminology when pike formations required soldiers to protect the rear ranks with backward-facing weapons.
Medieval armies had to worry about attacks from all directions, so they developed specialized fighting techniques—the backspear fighter was essentially the bodyguard of the formation, defending vulnerable comrades!
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