scorched-earth policy
noun [ C usually singular ] uk/ˌskɔːtʃtˈɜːθ ˌpɒl.ə.si/ us/ˌskɔːrtʃtˈɝːθ ˌpɑː.lə.si/
焦土政策（军队毁掉某个地区的食品、建筑、设备等一切可能为敌所用的东西的政策）
the act of an army destroying everything in an area such as food, buildings, or equipment that could be useful to an enemy