"The better our defenses, the less likely we are to be attacked." - are you sure?
If an enemy was at all inclined to attack, and fearful of pre-emptive attack, would they not be MORE likely to attack their perceived foe as they are building up their defenses, hoping for vulnerabilities? Why wait until the system is perfected?
If a defense has been conclusively proven to be infallible, then that might discourage attacks, but only by rational enemies.