World War II: The US Army's 90th Infantry Division liberated Flossenbürg concentration camp (pictured) in Germany, freeing 1,500 prisoners.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

The 90th Infantry Division was a unit of the United States Army that served in World War I and World War II. Its lineage is carried on by the 90th Sustainment Brigade.

Flossenbürg was a Nazi concentration camp built in May 1938 by the SS Main Economic and Administrative Office. Unlike other concentration camps, it was located in a remote area, in the Fichtel Mountains of Bavaria, adjacent to the town of Flossenbürg and near the German border with Czechoslovakia. The camp's initial purpose was to exploit the forced labor of prisoners for the production of granite for Nazi architecture. In 1943, the bulk of prisoners switched to producing Messerschmitt Bf 109 fighter planes and other armaments for Germany's war effort. Originally intended for German "criminal" and "asocial" prisoners, the camp's numbers swelled with political prisoners from outside Germany and, after Germany's invasion of the Soviet Union, Soviet prisoners of war. It also developed an extensive subcamp system that eventually collectively held many more prisoners than the main camp.