Short answers, pulled from the story.
A scorched-earth policy is a military strategy of destroying everything that allows an enemy force to fight, including water, food, humans, animals, plants, and infrastructure. It can be used by a retreating army to leave nothing of value or by an advancing army to deny resources to guerrilla fighters.
Scorched earth against non-combatants was banned under the 1977 Geneva Conventions. The conventions prohibit attacking, destroying, removing, or rendering useless objects indispensable to civilian survival, including foodstuffs, crops, livestock, and drinking water installations, for the purpose of denying them their sustenance value.
The term was found in English in a 1937 report on the Second Sino-Japanese War, describing the tactics of retreating Chinese forces who burned crops and destroyed infrastructure to sabotage the logistics of the advancing Japanese army.
Emperor Alexander I's scorched-earth strategy rendered Napoleon's invasion useless by burning the countryside and denying the Grande Armee any means of living off the land. Napoleon arrived in a virtually abandoned Moscow that had been largely destroyed, and his army starved on the retreat as it marched back along a route that had already been burned.
Between 100,000 and 150,000 people perished during William the Conqueror's Harrying of the North in 1069, when his forces burned villages from the Humber to the Tees, slaughtered inhabitants, and destroyed food stores so survivors would starve through the winter. The area took centuries to recover.
Historian P. L. A. Goldman estimated that 27,927 Boers died in the concentration camps established by British forces under General Lord Kitchener during the Second Boer War of 1899-1902. Of those, 26,251 were women and children, more than 22,000 of whom were under the age of 16.