"Effective" means the aggression and seizure stops, and they retreat. Letters from oligarchs aren't changing anything.
They've had this effect: https://www.nbcnews.com/news/world/putin-orders-nuclear-dete...
They've had this effect: https://www.nbcnews.com/news/world/putin-orders-nuclear-dete...
But I might be terribly wrong, of course, and you are right. Mr. Madman might be out is his mind for a very long time, and he does not listen to anyone.