In old mainline of Be2 Najdorf black played 7. ... Be6 instead of, today practically automatic, 7. ... Be7. This is because 7. ... Be6 is today considered dubious due to this idea:
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1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Be2 e5 7. Nb3 Be6 8. f4 Qc7 9. g4 exf4 10. g5
I tried to find first game with this idea in Caissabase. First game with 9. g4 that I found was played between Julio Kaplan and Walter S. Browne in 1972. Before multiple players played 8. f4 but answered 8. ... Qc7 with less precise 9. O-O, 9. f5 or 9. Nd5. So my question is: did Julio Kaplan discover this 9. g4 plan or was he, at least, the first player to play it in grandmaster chess?