I have some questions about when Backstabber can be played.

Can he be played after I have declared 0 attackers?

Can he be played after they have declared 0 defense?

No to the first part as the player action window occurs after attackers are declared. If there are attackers, but no defenders, let the dog out to play.

Just to complete the given answer:

Rulebook says on page 18: "At least one unit must be declared as an attacker." But as you can see from the timing-structure for engagements on page 31, the first option to play Backstabber during the engagement is after you declared attackers - if you have no unit to declare here, you can not go to this action window.

What you actually can do is playing him if there are 0 defenders (as Niranth said) or after all opponent units resolved their strikes (because there is an action-window after every strike): so he must not fear to be destroyed by enemy units.

okay can we clarify this a little more…

what is the latest point in a battle the following units can be played

1 backstabber

2 admiral ackbar

3 human replica droid

Rogue 3 said:

1 & 2: Can be played during any Action window during an engagement. Check the flowchart in the back of the rule book for the location of action windows. The last point they can be played is the action window after the last remaining unit strikes.

3: Is put into play as a Reaction to winning the edge battle. As such, can only be put into play during an engagement immediately after the edge battle that you won. Note that Human Replica Droid is free (put into play) while Backstabber and Ackbar are not (play). If not using its Reaction, Human Replica Droid can still be played as normal during the Deploy phase.

The timing diagram on page 31 is very useful for determining when there are action windows. The cards themselves tell you how they may be played, as action s or reaction s, with the latter expliclity stating the triggering condition required.

Situation:

LS units are exhausted. DS has 2 ready units available, Fleet Navigator and Logistics Officer (both of whom have 1 resource), and a 1 resource objective still open. Can DS declare one of those units as an attacker, then use its resource to help summon Backstabber?

Sounds good in theory.

Absolutely.