I'm looking for a word or phrase that I'd use to indicate a "planned operational" kind of protest, rather than a "carry placards and form a crowd" kind of protest.
The nearest thing that comes to mind is flash mobs, where people have secretly preagreed to suddenly converge on some place, do a thing, and leave. But that's not the right thing here.
The kind of thing I have in mind is if, say, 5 people agreed a statue was offensive and they decided they'll arrive at 5 am on the morning of some major public event, surround it with plywood, graffiti the plywood as a protest, and leave.
Or they knew that a group of white supremacists would be at a BLM protest and agreed they'd all turn up with milkshakes to douse them, then hide them by standing in front with their own (larger) antifascist banners for the 3 hour duration of the event.
One of them might say to a friend, "How would you feel about doing a _____ (kind of protest) and cover that statue from public view next month?", or "I'm thinking of organising a ______ protest against the fascists next time".
If there's a difference US/UK, then UK slang preferred.