Does Warwick's attack trigger go on the chain even if there are no damaged units at that battlefield, and can you respond to it with reaction speed spells?

Ruling: Yes, Warwick's attack trigger goes on the chain when he moves to an occupied battlefield, even if there are no damaged units present. You can respond to this trigger with reaction speed spells before it resolves.

Sequence:

• Move Warwick to an occupied battlefield
• His attack trigger goes on the chain
• You hold priority and can place reaction speed spells on the chain
• Pass priority
• Opponent passes priority
• Reaction speed spell resolves
• Pass priority, opponent passes priority
• Warwick attack trigger resolves

Nuances:

• It is safer and more optimal to play reaction speed spells like Flurry of Blades before moving Warwick, or even while Warwick is still in hand before playing him
• If Warwick is killed before his trigger resolves, the ability still resolves but has no effect because it specifically targets units 'here' and Warwick is no longer on the battlefield