Chess Mentor story...

This is a position from a game played in Great Britain in 1951. Hugh Alexander, playing White, was the No.1 ranked British player from the 1930's to around 1960. He was an extremely dangerous tactician who defeated many of the world's strongest players of that era. What wasn't well known at the time was the role that he and several other of Britain's strongest chess masters played in defeating the Germans in World War II. Alexander and others were recruited into the code breaking efforts at Bletchley Park. There, working with such luminaries as Alan Turing he led the group which broke the German naval codes. Considered by many historians the critical factor in winning the Battle of the Atlantic, this effort enabled Allied convoys to evade the German submarine threat.
Efim Bogolyubov, playing Black, was twice the challenger for the World Championship. In both matches he was defeated by Alexander Alekhine. Bogolyubov had an interesting rise to prominence in chess. As a Russian citizen playing in a tournament in Mannheim, Germany in 1914, he was interned when World War I began. His fellow prisoners included many of the world's strongest masters. With nothing much else to do they organized tournaments amongst themselves. Given that high level of competition, Bogolyubov emerged as one of the strongest players in the world by the end of the war.
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White has a clear advantage in this position. He has excellent attacking chances on the kingside and Black's knight on a8 is very badly placed. Find the knockout blow.