If you use Zenith Blade to move a unit with a 'when attacking' trigger into an already existing showdown, does the when attacking trigger activate?

Ruling: Yes, the when attacking trigger activates, but only if you are the attacker in the showdown. If you are the defender, the when attacking trigger does not activate.

Sequence:

• Determine whether you are the attacker or defender in the existing showdown
• If you are the attacker: the unit's when attacking trigger activates when moved into the showdown
• If you are the defender: the when attacking trigger does not activate

Nuances:

• If your opponent started the showdown trying to conquer an open battlefield, you would be the defender and don't get the trigger
• If you started the showdown in any way and then move a unit with Zenith Blade, you will get the trigger
• This ruling is based on developer statements but may not be fully supported by current written rules (RAI vs RAW situation)