Why countries in Europe were nervous that other would attack them so they formed?

After the devastating effects of World War I and World War II, European countries sought to prevent future conflicts and promote cooperation. To achieve this, they formed alliances and organizations such as the European Union (EU) and the North Atlantic Treaty Organization (NATO). These alliances provided a framework for collective security, economic integration, and political cooperation, reducing the likelihood of war and fostering peace and stability in the region.