Raping and Pillaging
An undisciplined military style manoeuvre activated on enemy turf (or friendly turf if control totally lost) after any immediate enemy troops have been dispatched but before you make a run back to safe territory.
Although this technique had been known for some time, it was brought into the public's eye in BIG way by the Vikings around 800AD. Many other nations have tried to emulate these sea raiders with greater or lesser success. (The Mongols being the only race to equal or exceed the horned hat brigade).
Rape of female members of the targeted tribe/race is now used as a form of ethnic cleansing in places like the Balkans/Darfur. Any kids produced will be 'ethnically' of the rapers tribe/race.
Rape may also be used during interrogation to further weaken the captive. You can take this even further in bizarre ways as the Spams managed in Abu Grab prison in Iraq by sexually demeaning blokes in front of/using dogs, women, barnyard fowl etc.
How to do it:
Rape, theft, arson and torture are visited on the old, young, cattle, homes and property in a perm one from each column sort of a way. (some combinations are less likely than others i.e. torturing homes is rarely very satisfying or productive ... but raping cattle can be very satisfying)