Major wars are significant conflicts that involve large-scale military operations and often multiple nations. These wars can reshape borders, influence political systems, and impact societies for generations. Examples include World War I, World War II, and the Vietnam War, each marked by unique causes and consequences. The reasons for major wars can vary, including territorial disputes, resource competition, and ideological differences. They often lead to profound changes in international relations and can result in treaties, such as the Treaty of Versailles, which ended World War I. Understanding these wars helps us learn from history and strive for peace.