1br3r1/1Bp5/1pN1pB2/1P1RPPp1/2PPk1P1/K3Pp2/2b2P2/4N3 w - - 0 1
Addition to Alena’s analysis below:
- Rc5!! bxc5, 2. Nxb8+! (discovered check) c6, 3. Na6 cxd4, 4. Nc5#
I was solving this puzzle during one hour and I managed to get mate in 6. After that I decided to look at the position again. Suddenly I saw that I had forgotten to put the white rook on d5. As soon as I put it in place I solved this puzzle. Actually it was very easy.
Rc5 is a key move because it protects the king from check.