In both Ezekiel 38:18-39:6 and Revelation 19:11-21 the military forces are killed off before "the rest" are done in.
Babylon the Great is done in by human means. After that it is the 'kings of the earth and their armies' vs. Jesus and the heavenly armies. Then 'the rest are killed off by the long sword coming out of [Jesus]' mouth.'
By the way, their is a certain 'stragegic' logic to the 'battle plan,' if you will. Both the US and USSR had targeting priorities with their nuclear forces. These priorities were, generally, Counter-Force (which meant destroying high value military targets), Command and Control (including national leadership) Economic/Population Centers (which would include cities and other important infrastructure - which might also include dams, nuclear plants, depots, etc.) The amount of forces available to employ would have an impact on target choice. And, of course, their would be some expected overlap (E.G. a military base near a big city).
The idea of totally annihilating the population is not as common today, and it wasn't the strategic aim of the nuclear nations, but it may well have been an indirect result due to the nature of the weapons being employed. I think the idea of totally destroying a poulation would have not been so unheard of in the ANE.
In both Rev and Ezek the military forces are done away with first (and some accounts, such as Ezek 38/39, Zech 14 etc - picture military forces being caused to turn on each other), national leadership is ended/collapses, then sweep up operations against individuals. Interestingly, Rev 6:15-17 depicts people from all walks of society fleeing or hiding in caves and hills. As if cities, as population centers, were targeted, forcing people to flee elsewhere. No doubt, some of this is figurative.
As Spock would say, I'm not attempting to consider the moral implications of any of this, just taking a detatched look at it from a strategic planning perspective. There is a logic to the way the foretold destruction takes place. A logic that human military planners have also seen fit to use.