The bug that helped a supercomputer defeat a chess champion
In 1997, IBM's Deep Blue defeated World Chess Champion Garry Kasparov. During one critical game, a software glitch caused the machine to make a completely random move when it couldn't decide on a strategy. Kasparov, misinterpreting this erratic move as a sign of deep, superior intelligence, became flustered, which ultimately contributed to his defeat.
The Rematch in New York
In May 1997, reigning World Chess Champion Garry Kasparov sat down in New York City for a six-game rematch against Deep Blue, an IBM supercomputer. A year earlier, in Philadelphia, Kasparov had defeated an earlier version of the machine by a score of 4–2, despite losing the very first game. Following that initial contest, IBM engineers heavily upgraded the hardware and chess evaluation routines, doubling the computer's search speed to roughly 200 million positions per second.
Kasparov had long prepared for traditional human opponents by studying their psychological weaknesses, past games, and tactical habits. Facing a machine stripped away many of these psychological cues, forcing the grandmaster to play in an unfamiliar conceptual landscape. Despite the technological improvements IBM introduced, the defining turning point of the match stemmed not from calculating power, but from an unintended flaw in the machine's code.
A Fail-Safe Move in Game 1
Kasparov won the opening game of the 1997 match, steering the board into complex, closed positions where computer search algorithms typically struggled. Toward the end of the game, Deep Blue found itself in a completely lost position. Facing time constraints and unable to find a viable path through its standard search tree, the supercomputer encountered an internal software bug.
To prevent the machine from freezing or forfeiting on time when an unexpected condition occurred, IBM's programming team had built in a fail-safe routine. When the engine failed to resolve its search properly, the system selected a completely random valid move from its available options. Deep Blue moved a rook to an seemingly illogical square, and Kasparov quickly forced its resignation on the very next turn.