Do abilities that trigger when a unit attacks/defends alone trigger if the unit initially attacks/defends with other units, but then becomes alone after another unit is removed?

Ruling: No, abilities that trigger when a unit attacks/defends alone do not trigger if the unit becomes alone after already gaining the attacker/defender designation with other units.

Sequence:

• The unit must simultaneously gain the attacker/defender designation AND be the only unit at the battlefield for the trigger condition to be met
• If a unit gains the attacker/defender designation while not alone, the trigger condition is not satisfied
• If another unit is later removed, making it alone, the condition does not retroactively trigger because the unit already has the attacker/defender designation

Nuances:

• This is different from general "when I attack" or "when I defend" triggers, which only occur once per showdown regardless of other circumstances
• All conditions of a trigger must be satisfied simultaneously for it to evaluate