Is attacking mandatory if a unit is in combat?

[themortalgod]

If a unit is in combat during the combat phase, is it mandatory that you attack with it? The core rules aren't really clear. It seems like thats true, but I'm wondering if I was wrong. For example say a situation where my powerful centerpiece model is charged by a Jabberslythe. I'd prefer not to attack then just retreat during my turn. If my model attacks, odds are good it will either kill itself or take severe damage from the Jabberslythe. 

[RuneBrush]

I've had this in the past and it can actually be read in a number of ways.

The key pieces are "Any unit that has charged or has models within 3" of an enemy unit can attack with its melee weapons in the combat phase".  This implies that it's actually optional.

"The player whose turn it is picks a unit to attack with, then the opposing player must attack with a unit, and so on until all eligible units on both sides have attacked once"  This bit however suggests that if I attack, my opponent has no option to attack.

Generally I tend to play it that my opponent can select a unit and then simply make no attacks, especially if they're planning on retreating, however I'm not actually sure and to my knowledge it's not been FAQ'd

[Sheriff]

I thought not. I've opted to not attack some flagellants before as I did not want to make them mad at me. 

[themortalgod]

Just now, RuneBrush said:

I've had this in the past and it can actually be read in a number of ways.

The key pieces are "Any unit that has charged or has models within 3" of an enemy unit can attack with its melee weapons in the combat phase".  This implies that it's actually optional.

"The player whose turn it is picks a unit to attack with, then the opposing player must attack with a unit, and so on until all eligible units on both sides have attacked once"  This bit however suggests that if I attack, my opponent has no option to attack.

Generally I tend to play it that my opponent can select a unit and then simply make no attacks, especially if they're planning on retreating, however I'm not actually sure and to my knowledge it's not been FAQ'd

Yeah, that seems like a reasonable interpretation, though it is a huge grey area.  Other use cases would be situations where a unit is within 3" but you don't want to pill in and sacrifice zone control.

[RuneBrush]

Just now, themortalgod said:

Yeah, that seems like a reasonable interpretation, though it is a huge grey area.  Other use cases would be situations where a unit is within 3" but you don't want to pill in and sacrifice zone control.

Makes perfect sense.  An out of coherency unit has to attempt to regain coherency if they move too, so there is a precedence for not piling-in in the combat phase.

[Yeled]

From the Rules FAQ:

Q: Can I choose not to attack with a model, or not to use one or more of a model’s weapons when it attacks?

A: Yes.