A common mistake when writing adventures set in deserts is to assume that the climate is too ferociously hot to wear armor. Historically, most battles in deserts involved troops dressed in protective armor. Although they would have been miserable during the hottest part of the day or the hottest part of the year, desert weather isn't intolerably hot 24/7.
During battle/war the heads of all slain are decapitated and collected by the slayer. The slayer will clean them up and put them on display for inspection by the commander. Depending on the deads name, rank, and expression on the face held by the death blow-the slayer will be rewarded by gold and/or status.