How do you differentiate which 'when attacking/defending' effects trigger only during the initial attack/defense declaration versus effects that trigger when a unit becomes an attacker/defender later during the action phase?

Ruling: All "when attacking" and "when defending" triggers happen when a unit gains the Attacker or Defender designation, which occurs during a cleanup step. The timing of when the trigger is added to the chain depends on whether the unit was already on the battlefield or joined mid-fight.

Sequence:

• If the unit is already at the battlefield when it gains Attacker/Defender status, their trigger goes on the Initial Chain
• If the unit joins mid-fight and gains Attacker/Defender status, the trigger gets added to the current chain or creates a new one

Nuances:

• Effects like "when a unit attacks alone" check the condition at the time the trigger would occur; if a unit already had the Attacker condition before becoming alone (e.g., another attacker died during action phase), the "attacks alone" trigger would not occur since the unit already had the attacking condition prior to being alone