Re: I have a cunning plan...
Well, as one who is retired US military, I'll mention the fact that we were only armed when in the field training or on the range firing, when on our home base.
So, going to and from my home to the base, I most certainly was not armed.
That said, if anyone then or now came at me with a knife, he'd end up either with multiple dislocations or impaled upon his own blade. It all would depend on how irritated I was.