As high-value orbital regions become increasingly congested, pursuit–evasion confrontations among spacecraft have emerged as a critical issue in the field of space security. Active defense strategies, in which a target spacecraft releases defensive vehicles to implement counter-interception against the pursuer, constitute a three-body engagement scenario involving the target, the pursuer, and the defender. However, in actual engagements, the presence of observation noise, incomplete information, and multi-strategy adversarial conditions arising from uncertain pursuit policies render existing guidance methods—whether based on unilateral optimal control, differential games, or conventional reinforcement learning—incapable of simultaneously addressing the multiple challenges posed by unknown pursuit strategies, information deficiencies, and high-maneuverability confrontations. Consequently, how to achieve cooperative adaptive guidance between the target and the defender under conditions of incomplete observations and variable pursuit policies has become a key technological bottleneck for enhancing spacecraft survivability.