Bobby Fischer may be your idol, but the early masters bear some close study

Many gifted chess players achieve considerable success and then reach a plateau that seems to defy all their efforts at further improvement. Often the problem arises because of the player's insecure chess foundation and understanding. The answer often is ''Back to Basics!'' I have overheard conversations of younger players which gave the impression that they felt that all chess began with Bobby Fischer. Actually, Fischer's great strength arose from his complete mastery and study of the early masters.

We Americans are fortunate in that we have a great chess tradition. This summer we will observe the centenary of the death of Paul Morphy, who dominated the world of chess more than a century ago. His positional logic and open game strategy laid down important principles for obtaining advantages.

Harry Nelson Pillsbury of Somerville, Mass., established himself as Morphy's successor, the de facto American champion, when he journeyed to Hastings, England, in 1895 and astounded the chess world by winning first prize ahead of a host of superstars, including the new world champion, Emanuel Lasker. When Pillsbury passed on at the age of 33, considered a major loss to the world of chess, his lifetime record against the great Lasker stood at 7-7.

A contemporary of and successor to Pillsbury was Frank James Marshall, the last romantic of chess, who loved an open game, always played for mate, and believed that the best defense is a good offense. Today's game depicts Marshall destroying Pillsbury in a modern opening.

Actually it was slaughters of this type that kept players from playing the fianchetto defense. Now, 80 years later, when the principles of the defense are better understood, this opening enjoys considerable popularity.

Pirc-Robatsch Defense Marshall Pillsbury 1. P-Q4 P-Q3 2. P-K4 N-KB3 3 N-QB3 P-KN3 (a) 4. P-B4 (b) B-N2 5. P-K5 PxP 6. BPxP N-Q4 7. N-B3 N-QB3 (c) 8. B-QB4 P-K3? (d) 9. B-KN5! NxN 10. PxN N-K2 11. O-O P-KR3 12. B-B6 (e) BxB 13. PxB N-B4 14. Q-K2 QxP (f) 15. P-N4 (g) N-Q3 16. N-K5 Q-K2 17. B-Q3 O-O 18. R-B2 K-N2 19. QR-KB1 B-Q2 20. R-B6 (h) R-KN1 21. NxNP QxR (i) 22. RxQ KxR 23. Q-K5 mate (j)

A. Pillsbury was one of the first great players to experiment with the fianchetto of the KB.

B. True to his style, Marshall selects the most aggressive continuation for White.

C. More accurate was 7. . . . O-O. Then 8. B-QB4 could be well met by 8. . . . NxN; 9. PxN, P-QB4, striking out at the White center.

D. In a large sense this might be considered Black's losing move. It creates holes and irremediably weakens his dark squares.

E. Very good. White does not worry about the possible loss of his advanced pawn, as the open KB file will be a winning avenue for attack.

F. Undeniably risky, but probably unavoidable in the long run.

G. It is important for White to strike immediately before Black can play 15. . . . P-KR4, which would offer prospects of a successful defense.

H. Black cannot now get fair value for the Queen with 20. . . . QxR, since his QB at Q2 is loose. The threat is now 21. NxNP.

I. No better is 21. . . . PxN; 22. RxP ch.

J. Certainly an artistic mate.