[Retric]

And yet after the invention of the gun attacking a prepared defensive positions often results in fewer casualties.

Defensive structures offset but don’t eliminate the advantage of initiative, especially when you start talking about a lone defender who needs to sleep etc.

[locutous]

Manoeuver has always been useful. Modern mobility and arms haven't changed that. Gaining superior firepower or leverage at the decision point is the real take away, not who is attacking or defending. Fixed structures are always an asset, but you still have to recognize that it doesn't eliminate the need for intelligence and superior strategy.

Your conclusion about defense being essentially useless is still dead wrong.

Once the first few home invasions, rapings, and pillagings of sleeping residences have occurred. Word will spread. The would be invaders will encounter a round the clock watch setup by a neighborhood or family that invited all their cousins and can afford a 24/7 watch, with dogs, home made alarms, and man traps.

And those attackers will have the fight of their lives on their hands. Once their surprise element is gone, they lose the initiative to things they can't anticipate without serious new intelligence and all advantage is now reversed and you enter the counter attacking and ambush scenarios which you pointed out, are very effective.

[Retric]

> defense being essentially useless is still dead wrong

That’s not my conclusion, it’s that defense roughly counters the otherwise overwhelming advantage of attackers.

> round the clock watch watch setup by a neighborhood

That’s assuming a great deal of cohesion in your post apocalyptic scenario. I have no problem saying large communities provide a significant benefit, but that’s a product of a working society not something you would see after say a disease kills off 99.9% of the population.