The increasing pace is the clearest proof it’s all bluster. He gets a small window to act while people try to make sense of his threat and by the time they realize it was just bluster he hopes to accomplish whatever he is trying to accomplish.
Yes, he has to get at least one major city or region under his control before he can decide to end the hostilities. That’s all he is left with now, is obtaining some kind of symbolic victory that he can try to sell domestically.