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I'll explain it step by step:
1) It doesn't depend on anything. Even if you hold the defense for a long time, the attacker will gain experience.
2) Are you saying that if you develop an attack plan and start executing it, any deviation from the plan will completely disorient the enemy? Like, you break through a line, but then you see that you're short three soldiers, and because of that, the plan falls apart, so you retreat?
3) A counterattack will happen in any case. Not immediately, but if the defenders have the strength and a chance of success, and if they haven't been completely wiped out, then a counterattack will definitely happen.
Answer to P.S.: A counterattack is a measure taken by the attacking side, believe me.
Answer to P.P.S.: In this case, defense is a tactic of isolation and neutrality. First, people will interact with each other much less. Second, it's like a time bomb: cities grow, and no one cares about the environment – production with massive pollution is the most economically viable, and environmentalists will be on the defensive – after all, everyone is defending themselves; we can't say that it's wrong to harm nature; that would be an attack on the rights of producers! Then things will get worse: overpopulation, famine, economic crises... And all because someone didn't assert their rights in a sufficiently aggressive way at the time.