The strategy was that you should initially cooperate and then reciprocate your opponent i.e. start by being nice and then do what your opponent did to you last time - also known as direct reciprocity.
La estrategia era que inicialmente debías cooperar y entonces reciprocar a tu oponente, es decir, empezar siendo bueno y entonces hacer lo que tu oponente te haya hecho la última vez (reciprocidad directa).