The main and common factor that caused countries to join the United Nations was the desire for collective security and the promotion of peace and stability in the world. After the devastating effects of World War II, countries recognized the need for a global organization that could prevent future conflicts and promote cooperation among nations. The United Nations was established with the goal of maintaining international peace and security, promoting human rights, and fostering economic and social development. Countries joined the UN to work together to address global challenges and build a more peaceful and prosperous world.
