World War II: In retaliation for the massacre of captured Americans by Waffen SS soldiers, U.S. Army personnel killed an estimated 80 Wehrmacht prisoners near Chenogne, Belgium.

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 Malmedy massacre was a German war crime committed by soldiers of the Waffen-SS on 17 December 1944 at the Baugnez crossroads near the city of Malmedy, Belgium, during the Battle of the Bulge. Soldiers of Kampfgruppe Peiper summarily killed eighty-four U.S. Army prisoners of war (POWs) who had surrendered after a brief battle. The Waffen-SS soldiers had grouped the U.S. POWs in a farmer's field, where they used machine guns to shoot and kill the grouped POWs; many of the prisoners of war who survived the gunfire of the massacre were killed with a coup de grâce gunshot to the head.

The Waffen-SS was the combat branch of the Nazi Party's paramilitary Schutzstaffel (SS) organisation. Its formations included men from Nazi Germany, along with volunteers and conscripts from both German-occupied Europe and unoccupied lands. With the start of World War II, tactical control was exercised by the Oberkommando der Wehrmacht, with some units being subordinated to the Kommandostab Reichsführer-SS directly under Reichsführer-SS Heinrich Himmler's control. It was disbanded in May 1945.