It was fought between Spanish soldiers and Apache warriors, near the Presidio Santa Cruz de Terrenate in the present day southern Arizona.

The site for El Presidio Santa Cruz de Terrenate, near the middle of the San Pedro River, was chosen on August 22, 1775 by Colonel Hugo O'Conor (born in Ireland) who was in charge of relocating Spanish fortifications on the Sonoran frontier.

Several adobe-walled structures and jacals were also constructed to house the families of the garrison soldiers, along with a small barracks, an officer's quarters, a chapel and a plaza.

The Spaniards did not have long to wait before hostile Apaches began to harass the settlement, attacking anyone who ventured out for water or those who tried to plant crops in the nearby fields.

(see http://www.seymourharlan.com/My_Homepage_Files/Page93.html) The battle took place along the San Pedro River, at some distance from the uncompleted fort, and it left the commander and 29 of his men dead after a long fight.