Are all attacking units in an engagement still required to focus to strike and exhaust (get one of the tokens) even if there are no defenders?

Or do they just win the engagement and allocate damage to the objective if necessary?

Say for example 1 unit has 1 DMg he can do to objectives and another unit can only damage units. Id assume in order to get the DMg for the objective he would have to strike, but the unit that can only DMg units doesn't need to strike correct?

If they are able to be focused, they MUST focus. Even if they do nothing, they were still involved in the battle. Maybe they drove the bus to the front lines?

Ok, so units in an engagement always focus. Thanks!

And an add-on, after a unit has focused to strike, if an event or reaction causes it to shed it's focus token(s) while still in that engagement, then it must strike again.

this might happen more often with cards like lando. if, for instance, there is 3 DS defenders against 1 LS attacker, and the LS has lando out, he can then spend a single resource and remove his attacker from the battle leaving all 3 defenders to continue the battle, thereby forcing them to focus even though there is nothing for them to do, unless they have any tactics icons which could still be placed.