In 1967, a book, The Report from Iron Mountain, was published and it details the analyses of a government panel that concludes that war, or a credible substitute for war, is necessary if governments are to maintain power. There is still controversy whether the book was hoax or factual.
Fact or fiction, the conclusion of the book, namely that war is necessary for both a vibrant economy and the necessity of government control, seems to have guided US foreign and domestic policy since World War II.
Since World War II, the US has been involved in 14 military operations, all initiated by the US without having been attacked by the country in which the US intervened. Afghanistan harboured a terrorist organization that organized the 911 incident but 911 was not financed or promoted by the Afghan government.
Here below a list of US interventions that do not include the most recent, Syria, to combat ISIL: