Six seconds! That’s how long Radjabov had to choose his next move in the diagram below, from an online rapid game in 2021. Plausible options are 1 Kd3, 1 Kd2 and 1 Kc3, but two of these lose by force. Radjabov picked a dud:
Teimour Radjabov-Hikaru Nakamura
Meltwater Champions Chess Tour Finals 2021
48 Kd2? Ke5! The only winning move. 49 Kd3 Kd5 White resigns, because he is in zugzwang – any move allows Black’s king a decisive intrusion. Only 50 Kc3 prevents Kd5-c4, but then 50…Ke4 51 Kd2 Kf3 mops up the kingside.
The immediate 48 Kd3 direct also loses to Kd5!, reaching the game’s final position one move faster. The only saving move in the diagram is 48 Kc3! Then 48…Kd5 49 Kd3! Ke5 50 Kd2! Ke4 51 Ke2! blocks the Black king and maintains the balance. The crucial insight is that White’s king position must ‘correspond’ to Black’s, i.e. Black Ke4 is met by Ke2, and Kd5 is met by Kd3. Therefore if Black plays …Ke5, (eyeing up both Ke4 and Kd5) White must respond with Kd2 (to defend with Ke2 or Kd3 respectively). Thus, in the diagram, only 49 Kc3! draws. Then 49…Kd6? 50 Kd4! seizes the initiative, so Black must instead choose 49..Kd5 or 49…Ke5, and White moves to d3 or d2 respectively.
I daresay Radjabov would have figured this out comfortably given 30 seconds. But some ‘corresponding square’ scenarios are far harder to fathom. The position above arose in the recent US Championships. If White manages to trade pawns with f3-f4, the win becomes straightforward, so Black must prevent that by playing …Kf5 whenever White plays his king to e3. Similarly, a White king move to c3 must be met by …Kd5 to prevent a queenside intrusion. From d2 White could reach either e3 or c3, so Black must respond to Kd2 with …Ke6. We can fill in the map of correspondences as follows: (e3gf5), (d2ge6) (e2gf6) (c3gd5) (d1ge7) (c2gd6).
Xiong’s last move, 51 Ke2-e1, posed Sevian a subtle question. On the next move, White could access d2, e2 or d1, and Black must be able to respond with …Ke6, …Kf6 or …Ke7 respectively. Therefore only …Kf7 keeps all those options open. Sevian chose wrongly, and his position was lost by force.
Jeffery Xiong-Samuel Sevian
US Chess Championships, St Louis, 2026
51… Kf5? 52 Kd1 Kf6 52…Kf4 is tempting, but 53 Ke2 Kg3 54 Ke3 Kxh4 55 f4! exf4+ 56 Kxf4 Kh3 57 d4 wins, e.g. 57…h4 58 d5 Kg2 59 d6 h3 60 d7 h2 61 d8=Q h1=Q 62 Qd2+ Kf1 63 Qd1+ Kg2 64 Qe2+ Kh3 65 Qg4+ Kh2 66 Qg3 mate! 53 Ke2 Ke6 54 Kd2 Kf6 55 Kc3 Kf5 56 Kc4 Kf4 57 Kd5 Kf5 58 Kc5 Kf4 59 Kd6 Kf5 60 Ke7 Black resigns
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