The Cambodian genocide

The massacres ended when the Vietnamese military invaded in 1978 and toppled the Khmer Rouge regime. By January 1979, 1.5 to 2 million people had died due to the Khmer Rouge's policies, including 200,000�"300,000 Chinese Cambodians, 90,000�"500,000 Cambodian Cham (who are mostly Muslim), and 20,000 Vietnamese Cambodians. 20,000 people passed through the Security Prison 21, one of the 196 prisons the Khmer Rouge operated, and only seven adults survived. The prisoners were taken to the Killing Fields, where they were executed (often with pickaxes, to save bullets) and buried in mass graves. Abduction and indoctrination of children was widespread, and many were persuaded or forced to commit atrocities. As of 2009, the Documentation Center of Cambodia has mapped 23,745 mass graves containing approximately 1.3 million suspected victims of execution. Direct execution is believed to account for up to 60% of the genocide's death toll, with other victims succumbing to starvation, exhaustion, or disease.

Total War: A new way of conducting war appeared during the Civil War. Instead of focusing only on military targets, armies conducting total war destroyed homes and crops to demoralize and undermine the civilian base of the enemy's war effort. (Sherman in Georgia or Sheridan in the Shenandoah Valley, for example.)

Ironclad: A ship protected by iron armor.

Drill: To practice marching, military formations and the steps in firing and handling one's weapon.

"Quaker Guns": Large logs painted to look like cannons; used to fool the enemy into thinking a position was stronger than it really was.

Abolitionist: Someone who wishes to abolish or get rid of slavery.