Last night at the dojo was all tanto waza, knife attacks and defenses.
My first learning was that I don't know anything about fighting with a knife or defending against an attacker with a knife.
The other thought I had was that you could be defending against what starts as an empty hand attack and the attacker could bring a knife into play at any time.
Tie those two thoughts together and it seems it would always be better to run.
This may not always be a choice.