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.

Flying Battery: A system where several horse-drawn cannons would ride along the battle front, stop and set up the guns, fire, limber up, and ride to another position. This practice gave the impression that many guns were in use when only a few were actually being used.

Ratify: To formally approve or sanction.

Lunette: (pronounced loo-net) A fortification shaped roughly like a half-moon. It presented two or three sides to the enemy but the rear was open to friendly lines.

Fortification: Something that makes a defensive position stronger, like high mounds of earth to protect cannon or spiky breastworks to slow an enemy charge. Fortifications may be man-made structures or a part of the natural terrain. Man-made fortifications could be permanent (mortar or stone) or temporary (wood and soil). Natural fortifications could include waterways, forests, hills and mountains, swamps and marshes.

Navy: A branch of the military using ships to conduct warfare. During the Civil War, "blue water" ships cruised the oceans and "brown water" boats floated up and down the rivers.