The evidence for obsidian use in conflict in the Andes comes from a variety of archaeological and ethnohistorical sources, but it is primarily in the form of indirect evidence. The data reveal a great expansion in the production of small obsidian projectile points after the onset of a food producing economy. The majority of Late Horizon weapons that the Spanish faced during their invasion appear to have been bola stones and percussion weapons like maces and slings(Cahlander, et al. 1980;Korfmann 1973), as well as padded armor.
Archaeologists working in the south-central Andes vary historically in their assessment of the use of projectiles in the highland region(Giesso 2000: 43). Bennett(1946: 23)asserts that the use of bow and arrow were not important on the altiplano, Metraux(1946: 244-245)says that spear throwers were in use, while Kidder(1956: 138)indicates that evidence from projectiles show that arrows were widely used at Tiwanaku. Of the projectile points analyzed by Giesso from Tiwanaku, 19% were made from obsidian, with the highest concentration of points coming from excavations in the civic/ceremonial core at the Akapana East, K'karaña, and Mollo Kontu mounds(Giesso 2000: 228-238).
In a dramatic example of obsidian use as a weapon, one archaeological findError! Reference source not found.shows a probable spear or dart point penetrated the victim's abdomen from the left anterior abdomen and lodged on the anterior side of the lumbar vertebra.