War can be defined as an armed conflict between political communities, whether between states or groups within a state. Classical war refers to international conflicts between states, while civil wars occur within states between rival groups. Terrorism involves the use or threat of violence against governments, organizations, or individuals to achieve political, religious, economic, or social goals. In modern wars, the majority of casualties are civilians, not combatants. Wars often have severe and long-lasting psychological and physical impacts on civilians and combatants alike and contribute to issues like post-traumatic stress disorder.