When someone asked Abraham Lincoln, after he was elected president, what he was going to do about his enemies, he replied, "I am going to destroy them. I am going to make them my friends."
To his enemies the householder must be a hero. Them he must resist. That is the duty of the householder. He must not sit down in a corner and weep, and talk nonsense about non-resistance. If he does not show himself a hero to his enemies he has not done his duty.
As they were during the Cold War, urban population centers remain the most likely targets of a nuclear attack. Now, however, an attack may come without warning from an unknown enemy, to achieve unclear motives.