Morale check after step losses from assualt

[Poor Yorek]

Sorry, another question. All units from both sides? Or just the side that was the defender in the assault hex?

Just the one side would suffer a particular attack result.  So, as per example above, the American stack suffered a '2' result inflicted on it by the OpFor.  The American side, however, presuming that they were defending in that assault, would have had an assault factor of 6 (GO inf) + 2 (DIS ENG 5/2 round down) + 3 (DIS eng 5/2 round up) + 2 (DEM HMG 10/4 round down) +3 (DEM hmg 10/4 round up) = 10 12.  So a 9-col shifted up by 1 for undemoralized regular leader (and +1 for the undemoralized eng IF in a town or ENT hex) along with any other applicable modifiers.  

To keep it simple, then, assuming this was just an open terrain assault hex, this US stack would have rolled a 13-col defensive assault roll against the attack OpFor: this could have resulted in anything from a fizzle (-) result 6/36 times to a '2' result (1/36 times) that then would have been applied to the attacking side.  

So to summarize based on Daniel's post that the US stack had been assaulted in a open hex and had a '2' result inflicted upon them by the Attackers, the US assault defense could have inflicted: nothing; an M1; and M2; a '1'; or a '2' result that the Attacking Side would resolve separately.  Note any results of this defensive assault fire would stand the rest of the turn as the attacking side has used its action.

Hope this helps. 

Edit (I changed the rounding as per correction below, but left original for clarity)