According to Greek historian, Herodotus, the Amazons were a race of female warriors living on the Thermodon River in Scythia. There were no men in the community, and any boy born was killed or dispatched to his father beyond the river.
Hippocrates wrote that the girls had their right breast burnt off with hot irons such that they might better draw the bow. In the 3rd century AD, Roman historian Justin asserted that the mythological Amazon is derived from the Greek roots a (without) and mazos (breast). In Anabasis of Alexander, mention of the Amazons, said that their right breasts were smaller and were uncovered in battle. This observation could mean the legend of elective mastectomy was really right breast underdevelopment caused by deliberate binding or pinching.
Does it make sense that a mastectomy would make using a bow easier?
Actually it does. It's been observed that most competitive women archers are smaller breasted, and a chest guard is actually worn by many competitors to avoid inadvertent injury to their breast when shooting. The weight of the breast also changes the center of gravity and requires active extension of your lower back muscles to remain erect, a distinct liability for horseback based or hand to hand combat.
Among these legendary Amazonians were Queens Hippolyta, whose girdle Hercules was assigned to recover (sure sounds like a panty raid to me) as one of his 12 great tasks, Penthesilea for whose death Achilles mourned, and Thalestrias who had an affair with Alexander the Great.
In DC Comics, the famous Wonder Woman is supposed to be Diana, daughter of Hippolyta and Amazonian princess. For whatever reason she apparently did not get the memo about having small breast :)
Factoid to store away next time you're a contestant on Jeopardy: Spanish conqueror, Francisco de Orellana named the Amazon River as such after encountering women warriors among the Indian tribes of South America.