Wars are large-scale conflicts between groups, often nations, that involve organized military forces. They can arise from various causes, including territorial disputes, political disagreements, or competition for resources. Wars can lead to significant changes in power, borders, and societies, affecting millions of lives. Throughout history, many notable wars have shaped the world, such as World War I and World War II. These conflicts often result in loss of life, economic hardship, and social upheaval. Efforts to prevent wars include diplomacy, treaties, and international organizations like the United Nations, which aim to promote peace and resolve disputes peacefully.