I'm thinking no since relentless happens "when you declair an attack" and is not actually part o the attack that can be blocked.
Obviously this only matters in the skirmish game where the strain would be turnd to damage. I know you can discard a command card to prevent strain from turning to damage during skirmish play, but I wanted to make sure it also couldn't be blocked by the dice.
In other words, I think if Relentless triggers in skirmish (i.e., you are within 3 spaces when you declair an attack), it does one auto-damage that can only be blocked if you discard a command card. Correct?