Security alliances are agreements between countries to cooperate on defense and security matters. These alliances aim to enhance collective security by sharing resources, intelligence, and military capabilities. A well-known example is the North Atlantic Treaty Organization (NATO), which was formed to provide mutual defense against potential threats. Such alliances can deter aggression by demonstrating a united front, making it less likely for adversaries to attack. They also facilitate joint training exercises and strategic planning, allowing member nations to respond more effectively to crises. Overall, security alliances play a crucial role in maintaining international stability and peace.