International alliances affect national security by enabling countries to collaborate on mutual defense, intelligence sharing, and crisis management. By forming alliances, nations can deter potential threats and enhance their strategic positioning through collective security agreements. This collaboration may also lead to shared resources, enhanced military capabilities, and coordinated responses to global challenges, such as terrorism or natural disasters. However, reliance on alliances can create tensions if member states have conflicting interests. Ultimately, international alliances play a crucial role in shaping geopolitical stability and ensuring national defense.