In war, a scorched-earth policy is defined as leaving nothing behind that an enemy might have use for — even if that means burning it all down.
This brutal military strategy can involve destroying nearly everything in a conquered region. A scorched-earth policy might mean wiping out stores of food, crops in fields, and water sources. During the Gulf War, Iraqi forces applied the policy when they set oil wells on fire as they retreated, so U.S. invaders couldn't seize them. Scorched-earth policy is used in business too, to mean making a company unattractive to potential buyers, in order to avoid a hostile takeover.