Anyone know of the origin of what I think might be called “total warfare” in that cities are basically destroyed rather than simply occupied? We can of course think of Carthage at the time of the Third Punic War, when Rome leveled it around 150 B.C. But last night I just heard of the story from 510 B.C., when the rival town of Croton (in southern Italy) conquered Sybaris and the channeled a river so that it ran over the defeated town, making sure it wouldn't rise again. Were there other instances of this kind of thing happening before this date?
Talking of total warfare can get kind of sticky. First, we have to define what we are talking about as in, what exactly do you mean by total warfare. The general definition accepted now is warfare in which all aspects of society are mobilized to defeat an enemy; economic, manpower, industry, food production are all given first to the military effort so that the state or nation can exert the maximum possible effort toward defeating their enemy. The typical example is pre-Napoleonic revolutionary France and the days of the Second Coalition and levee-en-masse. If however, you are just referring to the complete destruction of rival cities, that probably dates to prehistory. There is evidence that Trot was conquered and destroyed by fire repeatedly as earlier as 1500-1600 B.C.As to origins, that is simple and somewhat along the lines of "dead men tell no tales". A city that has been completely subjugated can no longer be a threat to whatever society won the contest. People have long memories and revenge is a strong motivator. If you kill or enslave everyobody and destroy a given town there can be no focus for revenge because that focus has been destroyed and scattered.
Didn't the Romans destroy Syracuse when they captured Sicily? I can also think of a few biblical examples such as Jericho, Sodom and Gomorrah, and the land of Canaan itself. The Hebrews conquered Canaan and enslaved or killed all the original inhabitants if I remember correctly. There is also Troy, which was put to the torch and destroyed after the Trojan War at least according to Homer.