World War I was significantly larger in scale than previous wars, involving more countries from around the world and resulting in unprecedented casualties of over 15 million. The mobilization of total war engaged entire populations and economies in a way that deeply impacted societies and laid the seeds for conflicts after the war. The Treaty of Versailles imposed punitive terms on Germany, contributing to tensions. The Cold War emerged from ideological differences between communist and democratic forms of government, dividing Europe and much of the world between Western and Soviet spheres of influence and raising fears of nuclear conflict for decades. The United Nations was formed with the aim of preventing future wars and promoting international cooperation.