[tweetle_beetle]

Defensive weapon is something of an oxymoron, apart from technologies like missile defense [1]. Putting that to one side, rational deterrence theory[2] suggests that:

(Probability of deterrer carrying out deterrent threat × Costs if threat carried out) > (Probability of the attacker accomplishing the action × Benefits of the action)

You could argue that Russia successfully destabilising the US (via Trump) and Europe (via Brexit and far right) is proof that nuclear missiles "pointed to the east" worked at defending against direct conflict and forced an alternative.

[1] https://en.wikipedia.org/wiki/Missile_defense?wprov=sfla1 [2] https://en.wikipedia.org/wiki/Deterrence_theory?wprov=sfla1