Emanuel Lasker v Wilhelm Steinitz, world championship match, New York 1894. Lasker held the world title for 27 years, a record which has never been broken, and his shrewdest move was right at the start when he persuaded the ageing Steinitz to accept him as a legitimate challenger. Steinitz should have met Lasker’s rival and enemy Siegbert Tarrasch, who dominated the big tournaments of the time. But Tarrasch dithered over taking time off from his Munich medical practice, while Lasker boosted his credentials by winning a series of matches against second-rate US and British opponents. So Lasker became the challenger, outplayed Steinitz in New York, then crushed him in a return in Moscow. Here White (to move) is knight and pawn down, but Black’s king is in trouble, How did Lasker achieve a winning advantage?