Compared with Anastasia’s mate, or an epaulette mate, the humble back-rank mate is named without imagination or whimsy. It is the Ronseal of mating patterns, administered by a rook or queen to a hapless king stuck on the rank behind its own pawns. But there is a rich variety of tactical motifs which culminate in this simple pattern, as shown by two of Magnus Carlsen’s recent games.

Dubov–Carlsen

FTX Crypto Cup Prelims, May 2021 (see left diagram)

Carlsen has just grabbed a pawn on e4, so the knight on d5 lacks support. The simple 21 Nc3 looks roughly equal, but Dubov launched a volley of tactics with 21 Qxe5. His idea was revealed after 21…Rf5 22 Qxd4 Bxd4 23 Rxc8, because after 23…Qxc8 24 Ne7+ White emerges a knight up. So Carlsen chose 23…Rxd5 24 Rxd8+ Rxd8 which at first sight looks like a quiescent equality. On closer inspection, White is in trouble, and one can pin the blame on back-rank mating ideas. For example, 25 Bc1 Bxf2! is disastrous, since e4-e3-e2 is coming, and 26 Rxf2? loses to Rd1+. Even nastier is 25 b3 Bxf2! 26 Rxf2 e3! 27 Bxe3 Rd1+ and wins. Dubov opted for a lesser evil with 25 g3 Bxb2 26 Bf4, but Carlsen smoothly converted the extra pawn: 26…b5 27 Re1 Rd4 28 Kg2 Rc4 29 Rd1 Bf6 30 Rd2 Kf7 31 g4 Bd4 32 Re2 Bc5 33 Rd2 Ke6 34 h4 a5 35 h5 a4 36 h6 gxh6 37 Bxh6 b4 38 Bf4 b3 39 axb3 axb3 40 Rb2 Rc3 41 Rb1 Kd5 White resigns

The FTX Crypto Cup was the latest online event in the Meltwater Champions Chess Tour. This season, Wesley So has defeated Carlsen in two previous finals, and he scored an important victory in their first blitz tiebreak game with a beautifully disguised back-rank mate idea (see below). But this time Carlsen got the last laugh, as wins in the final two games netted him the match, the title, $60,000 and 0.6 bitcoins.

Carlsen–So

FTX Crypto Cup Final, May 2021 (see right diagram)

The most urgent threat is c5-c4, so the pawn must be captured. In a blitz game it’s a tall order to assess the position which arises after 26 bxc5!? Rxb3 27 c6 Qb6 28 cxd7 Rd8. Instead, the game continued 26 Nxc5 Nxc5 and Carlsen thudded into the elephant trap with 27 Qxc5, whereupon So revealed the twist, 27…Rc6! Since 28 Qxc6 Qxc6 29 Rxc6 Ra1+ leads to a back-rank mate, White was forced to give up the queen. Carlsen tried 28 Rbc3 Rxc5 29 Rxc5, but with just rook and pawn against queen it was a lost cause, and White resigned ten moves later. Curiously, there was a path to salvation which exploits the weakness of Black’s back rank. From the diagram, 26 Nxc5 Nxc5 27 Rbc3!, and the latent threat of Rc3-c8+ recovers the knight. Since 27…Nd7 (to drop back to f8) 28 Rc7! wins the knight anyway, Black might as well settle for 27…Rxb4 28 Rxc5 g6 with an equal position.