I am writing a book in which the US government is planning an intervention in a 3rd world country in which we have over a trillion dollars worth of investments. Their authoritarian government is threatened and the media tells of the dangers of an overthrow and the possibly total loss of our investments - many of them by middle class investors saving for retirement. Just as our forces are mobilized one Trident submarine crew defects to the revolutionary government and the intervention is deterred. This submarine would represent less than 5% of the sea based firepower available to our government and yet would we have bombed Iraq if we were faced with 240 nuclear warheads carried by an indetectable vessel? If the greatest military power ever could be deterred with a small fraction of our firepower, what are the chances of a much weaker opponent taking their chances?
As a variation of the theme I would offer: it has nothing to do with national security and everything to do with national security budgets!