This was so hard. I believe the sequence starts with Re1+ forcing black to take, opening diagonal of bishop. Qxc2 sacrificing queen and opening C file. Nd4+ forces kb1 cause if Kd1 Nxb2 is checkmate. Nc3+ bxc3 is forced cause of Nc2 mate. Rb8+ king is forced to a1 after blocking with bishop at b7 and checkmate is delivered by Nc2. What a beautiful sequence.