How is 'collective defense' defined?

The concept of 'collective defense' refers specifically to a formal pact or agreement among member states to provide mutual support and defense if one of them is attacked. This principle underlies many international military alliances, with NATO being one of the most notable examples. The essence of collective defense is rooted in the notion that an attack on one member is considered an attack on all, thereby creating a unified response to aggression. This framework serves to deter potential aggressors, knowing that they would face a coalition of forces rather than a single nation.

In contrast, the other options relate to different forms of collaboration that do not specifically involve a military response to aggression. Sharing military intelligence, while important, does not constitute a promise of mutual defense. Economic cooperation focuses on trade and economic strategies rather than military security. Humanitarian efforts involve collaboration for non-military purposes, such as disaster relief, which diverges from the military obligations inherent in a collective defense agreement.