If I attack an occupied battlefield with a unit that has Assault +1 and my opponent plays Challenge against my unit during the combat, does my unit still have +1?

Ruling: Yes, if the battlefield is occupied, your unit will still have the +1 from Assault during the Challenge combat because your unit is considered attacking.

Nuances:

• This only applies when the battlefield is occupied, which initiates a combat
• If the battlefield is not occupied, moving to it initiates a showdown instead of a combat, and your unit would not be considered attacking (because there's no defender and no combat)