Game 4 of the Garry Kasparov-Deep Blue rematch ended in a draw after 56 moves when a weary Garry Kasparov was unable to capitalize on a late advantage.

"It was a tough game," said Kasparov minutes after the completion of the five-hour game. "I think I was winning at some point, but I didn't manage the position very well."

Kasparov, playing black, went into the endgame with a slight advantage over his computer opponent. But Deep Blue survived Kasparov's assault with a series of clever defensive maneuvers. "I believe it was a win for black," remarked Kasparov. But "I was tired and I couldn't figure it out. Obviously the position was winning at some point, but I couldn't finish it off."

The Deep Blue development team was more than happy to accept a draw. "For the last few hours, we were hoping we'd get the draw," said a relieved Murray Campbell. "Deep Blue was just hanging on for the last few hours."

Deep Blue, playing white, opened the game by moving its pawn to e4. It was the same opening move it used in defeating Kasparov in game two.

Kasparov's opening strategy took Deep Blue out of book -- that is, out of its pre-determined library of moves -- after the fourth move. The position was reminiscent of Game 2, commentator Maurice Ashley said. "Two center pawns, a blocked pawn chain, and white has space. In game two, white used the space to its advantage by not allowing Kasparov any room to breathe. Then Deep Blue strangled him to death." This time, though, Kasparov created his own space on the chessboard to maneuver.

As in the previous three games, Kasparov adapted his normal attacking style of play to a more passive approach against Deep Blue. But the world champion again seemed uncomfortable, playing a cautious, tactical game. "There's no way that Garry could expect to play superbly with this new style," said Seirawan. "He just didn't have enough time to adapt."

By mid-game, Deep Blue was ahead on material by one pawn, but Kasparov had more active pieces on the board.

Kasparov attempted to win back the pawn advantage by force during the endgame. Late in the game he succeeded. Deep Blue's pawns were now spread about the board - or isolated - in a weak position that gave Kasparov the advantage.

With 11 pieces left on the board - Kasparov had returned the extra pawn for a positional advantage - it was clear that Deep Blue had no chance for victory. "At this point, Deep Blue can only draw this game - at best," remarked commentator Michael Valvo. "Kasparov can win or force a draw, but unless he makes a tremendous blunder, there's really no way for him to lose."

Kasparov went on the offensive, aggressively attacking Black's pieces in an effort to win the game. The old Kasparov had once again emerged. But his effort fell short, and Kasparov offered the draw after Deep Blue's 56th move.

Kasparov was understandably disappointed that he failed to convert a slight endgame advantage into a win. Then again, he entered game four with low expectaions for a win. "I wasn't in a very good mood in the very beginning of the game," he said. "I didn't have big aspirations for the game playing the black pieces."