Anatoly Karpov sealed his 41st move in what looked like an advantageous position yesterday in the fourth game of the world chess championship match in Moscow. After the lull of the routinely drawn third game Tuesday, Karpov and 22-year-old challenger Gary Kasparov both came out fighting in yesterday's game. At the adjournment, Kasparov had a passed pawn and possible long-range chances, but Karpov seemed in a position to force a draw and possibly even a win. Kasparov is now leading by a score of 2-1.

The champion showed two qualities in the first session of this game: a willingness to take small risks (he did not castle until his 15th move) and a tenacious determination to work out his basic strategic plan (control of the b1-h7 diagonal) in spite of persistent tactical ploys by his opponent. In the opening, he managed to cramp Kasparov's position, particularly that of his queen's bishop, and finally precipitated an exchange that gave Kasparov a passed pawn. The trade-off, won through awkward but effective queen and bishop maneuvers, was Karpov's control of the white squares. In the adjourned position (pictured), with his queen and bishop lined up on the same diagonal, Karpov has a clear opportunity to draw through perpetual check and speculative shots at a winning position. To win, he will have to take a few risks, and the question that will be answered while he analyzes the position overnight is whether he will chance going for a victory.