Level Up (A5E) Shield Focus vs Defensive Weapon Property

[lichmaster]

That's an interesting caveat as any knockdown would only benefit mid level characters with multiple attacks or allies who could attack before the monster's next turn. I sort of dig the tactical choices that brings up. I need to read the wording of shield focus to see where that sits.

At least, that's how I read "when" entries. Maybe it's also ok to just say "I'm taking the attack action, but activate the bonus action immediately" and benefit from knockdown before the normal attack.
This gives a very significant edge in combat, which is why I'm reading it the way I do, but maybe someone else may clarify how to read "when" entries and confute my interpretation