In the match Petrosian started shakily, losing the first game and just escaping with a draw in the second game. From then on he was in control, and won the match (best of 24 games) by +5 –2 =15. In 1966 he defended the title against Boris Spassky, and won 12½–11½. The victory was rather more emphatic than the score suggests. In 1969 Spassky was again the challenger, and this time Petrosian lost 10½–12½.