There's a whole literature on the logic (and meta-logic) of deterrence called power transition theory that is worth looking into, as it sheds a lot of light on the unpleasant topic of nuclear deterrence and how that works.
In a more general sense, the solution to an elevated attack is not always a retaliatory attack, but perhaps a better defense that neutralizes it. Helmets can be used as weapons, but their primary purpose is to make weapons less effective and change the strategic calculus - now the enemy gets lesser results for the same effort, and either gives up or tires out and can be defeated with a smaller retaliation. In general, defense is thought to be somewhat stronger than offense, which is why surprise is so important. Technological edges tend to be negated over time.
Deeply understanding this takes a long time and a lot of study. Military science is a difficult but interesting subject, and tips over into systems theory.
In a more general sense, the solution to an elevated attack is not always a retaliatory attack, but perhaps a better defense that neutralizes it. Helmets can be used as weapons, but their primary purpose is to make weapons less effective and change the strategic calculus - now the enemy gets lesser results for the same effort, and either gives up or tires out and can be defeated with a smaller retaliation. In general, defense is thought to be somewhat stronger than offense, which is why surprise is so important. Technological edges tend to be negated over time.
Deeply understanding this takes a long time and a lot of study. Military science is a difficult but interesting subject, and tips over into systems theory.