Alliances: Agreements between nations to support each other militarily during times of conflict. For example, NATO is an alliance consisting of multiple countries committed to collective defense.
Total war: A concept where all aspects of society become fully engaged in supporting the war effort economically, politically, socially, and culturally. This includes rationing resources or conscripting citizens into service.
Treaty of Versailles: An agreement signed after World War I that imposed severe penalties on Germany, including territorial losses and financial reparations. It significantly shaped the geopolitical landscape leading up to World War II.