The major war characterized by the slogan "A War to End All Wars" is World War I, which lasted from 1914 to 1918. The phrase is often associated with President Woodrow Wilson, who envisioned the war as a means to make the world safe for democracy and prevent future conflicts of such devastating scale. The war involved intense trench warfare, significant loss of life, and the collapse of empires. Ultimately, while World War I led to significant political changes and the establishment of the League of Nations, it failed to prevent subsequent wars, including World War II.