scorched-earth policy

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The policy of devastating all land and buildings in the course of advancing or retreating troops so as to leave nothing salvageable to the enemy.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A military strategy that involves destroying buildings, crops, and other resources that could be useful to enemy forces.
• noun figuratively Any strategy that involves some type of drastic action.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the target company defends itself by selling off its crown jewels