be frightful with impunity
First of all, would you please read the following excerpts:
"Henry argued that Britain should warn Germany of reprisals for the next airship raid on London. 'The Hun,' he argued in the _Times_ in January 1916, 'is only formidable when he thinks that he can be frightful with impunity. "Blood and Iron" is his doctrine so long as it is his iron and someone else's blood.'"
I do not understand the second sentence, specifically its clause 'he thinks that he can be frightful with impunity'. Originally I thought 'frightful' to be 'Causing fright; terrifying'. The result of the induction was nonsense. Next, I considered it as 'Informal. Excessive; extreme: a frightful liar'. It made some sense to me though not full.
So now I try to rewrite that sentence like this:
"The Hun is only formidable when he thinks that he would not be punished till his intricities are full up."
Would you please comment on my Hun-like rewriting?
Thank you for reading the post.