Unit 7 covers the most destructive century in recorded history. The Ottoman, Russian, and Qing empires collapsed under internal and external pressure, opening space for revolutionary governments and new states. Imperialist competition, a tangled alliance system, and intense nationalism ignited World War I. The flawed peace settlement, the Great Depression, and the rise of fascist regimes then produced World War II. Both wars were total wars in which governments mobilized entire societies using propaganda, conscription, and new military technology. The interwar and wartime periods also produced mass atrocities including the Holocaust, the Armenian Genocide, the Holodomor, and later the Cambodian and Rwandan genocides.
Unit 7 is about why and how global conflicts erupted after 1900, how governments fought them, and what patterns of atrocity and instability they left behind. The core skill is causation: explaining which factors mattered most and why.
Why global conflict?The AP exam asks you to explain the relative significance of causes of global conflict from 1900 to the present. No single factor explains WWI or WWII. Militarism, alliance systems, imperialism, nationalism, economic crisis, and unresolved territorial grievances all interacted. The skill is building a defensible argument about which causes mattered most and why, using specific evidence from across the unit.