As I was studying one of my recently acquired tactics book it presented this crazy puzzle. The chapter theme was about 'the double attack'. I hate when you when see a simple looking puzzle like this when after a bit of assessment you find out it's an oddity to your current experience level and you're forced to have wrangle with it to find the solution. Anyway it's a puzzle composed by Troitzky in 1896.

well it isn't difficult to see that this is the ONLY move that can make any progress. In rook endgames activity is the key and you should always look for moves that activate your rook (in this case it wins immidiately but sometimes such moves are just a small part of a difficult endgame)