Garry Kasparov is a chess prodigy from Azerbaijan and a five-time world champion. On May 11, 1997, the world’s (then) greatest chess player in history was defeated by the IBM supercomputer, Deep Blue.

At that moment, artificial intelligence became an uncomfortable and yet ground-breaking reality.

Computers that could play chess had existed since the 1950s, but until 1985, they had little luck playing against humans. Feng-hsing Hsu, a student at Carnegie Mellon, developed a computer called Chiptest in 1985, which was designed to play chess at a more advanced level. In 1989, Hsu and a classmate went on to join a team of scientists led by CJ Tan at IBM that was working on developing Deep Blue, the supercomputer.

The scientists at IBM wanted to imitate the kind of thought patterns, the strong calculation and intuition that chess players rely on and develop over time. Kasparov, at the same time, became the youngest world champion at the age of 22.

In 1996, an arrogant Kasparov scoffed at the idea of a machine beating him, and defeated Deep Blue in their first chess series, declaring the superiority of human intelligence over artificial. He did, however, lose the first game before winning three and drawing two.

IBM then went back to work on Deep Blue, this time incorporating algorithms that could learn from older moves, thus bringing artificial intelligence even closer to resembling the human mind. By now, the supercomputer could calculate as many as 100 to 200 billion moves in the time a player got at the time to make a move.

In May, 1997, IBM challenged Kasparov once again with the new and improved Deep Blue. After six games, from May 3 to May 11, artificial intelligence won over human intelligence, marking one of the ground-breaking moments in the history of computer science, and of mankind.

Kasparov blamed his defeat on a single move by the computer, which, fifteen years later, turned out to be a bug in the computer’s software. This was pointed out in a book titled The Signal and the Noise published by New York Times journalist Nate Silver.

That single move, he said, was so sophisticated that it unsettled him. The move turned out to be completely random, caused by the bug. However, there is no saying that Kasparov would have won the match otherwise.