A
preventive war or
preventative war is a
war initiated to prevent another party from acquiring a
capability for attacking. The power being attacked has either a latent threat capability or has shown through its posturing that it intends to follow suit with a future attack. Preventive war aims to forestall a shift in the balance of power by strategically attacking before the balance of power has a chance to shift in the direction of the adversary. Preventive war is distinct from
preemptive war, which is first strike when an attack is imminent. Preventive war undertaken without the approval of the
United Nations is illegal under the modern framework of
international law, though
Robert Delahunty and
John Yoo from the
George W. Bush administration maintained in their discussion of the
Bush Doctrine that these standards are unrealistic.