Petrosian — Barcza

Interzonal TournamentStockholm, 1952

• Tigran Petrosian (1929–1984)The ninth World Champion, who held the title from 1963 to 1969 and was renowned for an airtight, risk-free defensive style.
• Gedeon Barcza (1911–1986)Hungarian grandmaster and eight-time national champion, known for the fianchetto setup that bears his name.

A pawn chain in the center can break down not only from a flank pawn's undermining moves. With a fixed pawn center, you always have to reckon with a minor piece sacrifice for two or three pawns. In that case the sacrificing side gets strong connected passed pawns in the center. Such combinations have occurred many times in practice.

This position arose after White's 23rd move. With the last move (23. a4), White aimed to strip the pawn on c4 of adequate support and so weaken Black's pawn chain.

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1. To the obvious reply
2. 23.
3. White has a strong continuation
4. 24.
5. An interesting undermining move
6. 24.
7. 25.
8. 26.
9. White's edge is clear — three excellent passed pawns for the piece. For example:
10. 26.
11. 27.
12. 28.
13. The source considers White simply winning here, but Black could give up the knight for a dangerous counterattack — the engine rates the compensation as sufficient
14. 29.
15. 30.
16. 31.
17. 32.
18. 33.
19. 34.
20. 35.
21. 36.
22. 37.
23. 38.
24. Typically, once the blockade breaks, White's central pawns rush forward unstoppably
25. The source treats 38. Rd1 as the natural continuation, but engine analysis shows 38. d7 won faster

Black avoided the advance 23...b4 and went from one danger straight into another:

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1. 23.
2. 24.
3. 25.
4. Now Black cannot play this move as in the previous variation, since it loses the rook on a8
5. 26.
6. 27.
7. 28.
8. And again the fixed center becomes mobile
9. 28.
10. 29.
11. Black resigned