He was a chess grandmaster, considered one of the best players never to become world champion. He was a four-time USSR champion, and ranked number one in the world in 1965. In 1976, he sought political asylum in the Netherlands after a tournament there. He progressed to the World Championship final in 1978 and 1981, but lost to Anatoly Karpov both times. He was the oldest active grandmaster in international tournaments for many years, and won the World Senior Chess Championship in 2006.