Armenian Tigran Petrosian is widely regarded as the best defender in the game of chess. He was the first person to demonstrate that it is possible to defend virtually every position. He was a brilliant tactician and an excellent strategic player. He could cope with every kind of situation.

Petrosian is most famous for being one of the best players pioneering the theory of prophylaxis. His style of play was often highly strategical, notable for anticipating opponent's possible attacks and he based many of his games on avoidance of error, content with accumulating small advantages.

In 1963 Petrosian defeated Mikhail Botvinnik 12.5–9.5 to become World Chess Champion. His patient, defensive style frustrated Botvinnik and if Botvinnik made one mistake, Petrosian was ready to punish him. Petrosian in 1966 defeated Boris Spassky 12.5-11.5 to retain his title.

Quote/s:
In those years, it was easier to win the Soviet Championship than a game against "Iron Tigran". — Lev Polugaevsky