This position comes from the game Sax-Ree 1984 and the position occurred after 20...Rfd8. The solution is 21. a4! Rxd4 22. axb5 Rxd1+ 23. Rxd1 and black resigns because the bishop has no moves and the queenside is falling apart. I saw this in a book and thought it was a nice puzzle.
After looking for a couple of minutes I'm going to go with 1. a4 Rxd4 2. axb5 Rxd1 3. Rxd1 gives black the open file and c6 looks super strong. 2... Rad8 3. Rxd4 Rxd4 4. Rxa7 seems even worse for black since he cannot use the open file to penetrate effectively to d2 or d1 and c6 is coming one way or another.
