Humans, and animals, often encounter ambiguous situations that require a decision on whether to take an offense or a defense strategy. Behavioral studies suggest that a strategy decision is frequently made before concrete options are evaluated. It remains enigmatic, however, how a strategy is determined without exploration of options. Here we investigated neural correlates of quick offense-versus-defense strategy decision in a board game, shogi. We found that the rostral anterior cingulate cortex and the posterior cingulate cortex complementally encoded the defense and attack strategy values, respectively. The dorsolateral prefrontal cortex compared the two strategy values. Several brain regions were activated during decision of concrete moves under an instructed strategy, whereas none of them showed correlation with defense or attack strategy values in their activities during strategy decision. These findings suggest that values of alternative strategies represented in different parts of the cingulate cortex have essential roles in intuitive strategy decision-making.