The environmental impact of war focuses on the modernization of warfare and its increasing effects on the environment. Scorched earth methods have been used for much of recorded history. However, methods of modern warfare cause far greater devastation on the environment. The progression of warfare from chemical weapons to nuclear weapons has increasingly created stress on ecosystems and the environment. Specific examples of the environmental impact of war include: World War I, World War II, the Vietnam War, the Rwandan Civil War, the Kosovo War and the Gulf War.