I don't beleive in 19....Na4 becouse of 20.Nxd5! Bxb2+ 21.Kc2 and white is threatning the Q and Ne7+.
We also have 19.... Na4 20.Nxd5 exd5 21.Rxd5 and again is white threatning the Q and if the Q moves, white have Rd8+......
Now is the question, what can black do in this position? The N nead to protect d5.
Originally posted by Gerrit de LeeuwI think 20. Ne4 is a nastier threat. It threatens 21. Nf6+ Bxf6 22. Qxf6 and the mate is inevitable then. If 20. ... dxe4, then simply 21. Rd8 and the queen is pinned. 20. ... Bxb2 21. Kxb2 Na4 22. Ka1and 22. ... Qb5 fails to 23. Qd8+ Bf8 24. Rh8+ so I still prefer 20. Ne4.
20) Be2, ... followed by 21) Rdh1, ... and 22) Rh8+, ...