King Prithvi Narayan Shah had difficulty conquering Kirtipur, whose site atop a ridge with two high points made it virtually impregnable.
The king had a shrewd adviser who came up with a very cunning plan. 
mnli hypothesis: The king had a shrewd adviser who came up with a very cunning plan.  premise: King Prithvi Narayan Shah had difficulty conquering Kirtipur, whose site atop a ridge with two high points made it virtually impregnable.