Petrosian had a special talent for prophylaxis. Nobody could do anything against him. As soon as someone began mobilizing their forces for an attack, Petrosian would see their plan and put it to rest. He rarely tried to initiate his own attacks. Often he would think only of his opponent's plans and stop them, leaving his opponents not knowing what to do. Eventually his antagonist would make some small error and Petrosian would pounce just like a tiger who has been lying in wait for just the right moment. This tendency earned him the name "Tiger". Petrosian defeated Botvinnik in 1963 to become the World Champion, until his downfall in 1969 to Boris Spassky.