Chomsky argues that as a part of this strategy, the U.S. has regularly engaged in "preventative war", which he highlights is illegal under international law and could be categorised as a war crime. Preventative war refers to conflict waged to prevent a nation ever reaching the stage where it could become a potential threat, and according to Chomsky, under the regimes of Ronald Reagan, George H.W. Bush and his son George W. Bush it has actively involved attacking "an imagined or invented threat" such as Grenada and Iraq. He differentiates this "preventative war" from "preemptive war", which he argues can be justifiable under international law in cases of self-defence.[23] Examining examples of preventative war waged by the United States, he notes that all of the nations that have been attacked have shared the same three characteristics: 1) they are "virtually defenseless", 2) they are "important enough to be worth the trouble" and 3) there has been a way to portray them as "the ultimate evil and an imminent threat to our survival."[24]