Can you use Retreat on a unit that you select with Cull?

Ruling: You can play Retreat as a reaction to Cull before Cull resolves, but not while Cull is resolving.

Sequence:

• If you only have one unit, you can Retreat it in response to Cull, leaving no units to kill
• If you have more than one unit, something will die even if you Retreat one unit

Nuances:

• The timing matters: Retreat must be played as a reaction before Cull resolves, not during its resolution