Oh, there was a threat. It's just that we're fighting the threat in THEIR backyard, not ours.
Who's backyard? Last time I checked, Iraqi civilians are still getting it in the neck. That's a completely invalid argument, anyway. We had Afghanistan for a terrorist sink anyway... funnily enough we still have it. Seems plenty big enough for all the insurgents to congregate.
The day the Iranians begin to dig a hole for an ICBM launcher, is the day a few Trident subs open their missile doors. However, I understand ICBM missile building is pretty tricky, and even super-powers have problems getting it to work. So relax, don't worry, and enjoy the sunshine. Or continue to hand-wring, desperately comparing 1939 to 2008 any which way you can. Your choice!

"We didn't start a war in time once, therefore we should always start one regardless of the circumstances at the slightest sniff of trouble!"