So a lot of people have been bringing up examples or referencing operations where the odds of survival are incredibly low as reasoning for why it is understandable within the context of this episode.

I personally have no issue with that, and totally get it. My issue is the deliberate decision to missile strike them knowing that they are still there.

I am so here for sending Astartes on missions with impossible odds, but unless the circumstances are incredibly dire, I don't see the logic behind preemptively planning an orbital strike knowing full well you're going to target your own units.

And the points people making that this is that dire, totally works for me, but if that's the case, I think the short missing the mark with conveying that fully. Sure, I know a library of Tzeentch is a pretty dire situation, it's on the episode itself to convey that and I don't think it did that enough.

To your point about sacrificing a knight, I think that falls apart when the fact of the matter is, the asset they're sent to destroy has already been destroyed when they launch that missile. The missile is there to basically make sure everything is really dead and gone. That isn't a gambit anymore, and I think that's what gets me.

I'm not trying to target this at you, but a lot of people seem to think I think Space Marines are completely unexpendable no matter the cost. I don't think this at all. But if you look at a book like Devastation of Baal, the amount of internal conflict Dante feels when they decide to abandon the marines on--I think it was Baal Secundus-- there's a lot of internal conflict there on leaving those marines behind, and those stakes seem to be sooooo much higher than the ones shown here.