Can you play Discipline with no units, and what happens if the targeted unit is killed in response?

Ruling: You cannot play Discipline with no units because you need a target. However, you can target an enemy unit if needed. If the targeted unit is killed in response, the card still resolves as much as possible - the unit won't get +2 but you still draw the card.

Sequence:

• You target a unit when putting Discipline on the chain
• If the unit is killed in response before Discipline resolves
• The +2 buff cannot be applied to the dead unit
• You still draw the card (resolves as much as possible)

Nuances:

• Discipline does not specify "friendly units" so you can target an enemy unit to get the draw effect