It might seem childish to say but once a pin (and the secondary safety is sweeped off) the only thing keeping the "spoon" (the little handle looking thing) from flying off is you're hand holding it. Did I mention there's a spring that makes it want to fly off? Let go, and the spoon flies off you have approximately 5-10 seconds to get rid of it! So every private who ever carried, or had to throw grenades has this little simplistic statement drilled into them. Holding onto grenades and letting them "cook off" is a really bad idea.
Once the spoon flies off, a small pin strikes a fuse which slowly "burns" down to a blasting cap, and the explosives inside. Now understand that the current M-67 Grenade is designed to kill everything in a 5 meter radius and and seriously wound anything in a 15 meter radius. the only way to avoid that is to jump on that grenade (actually something we were trained to do in basic. Drills would throw a grenade simulator and the closest man would dive on it to protect his buddies) sure you might be able to get away in time. Of course you just as likely might get killed while trying to get away. You either 1). throw it back, or 2). Jump on it. Option 3). let it go off ends in many people being killed.
The pin has been pulled so to speak on Iran. That the British and Our CJCS strongly urge against it, is pretty much beside the point. Israel can either strike, or wait till its too late. We should not only "let" them, but actually activly participate in helping them. Why? Well if the Shi'a state of Iran has Nukes, how long before the Saudis get them? Once they have them how long before Jordan and Syria, Egypt and Sudan, Hell I'm sure the Kuwaitis would feel pretty threatened, and Iraq, well they did fight a massive and costly 8 year war, I'm sure that they'd need nukes as well. In all seriousness, Iran having even one Nuclear warhead would be tantamount to pulling the pin on a grenade. Would the destruction reach America? Probably not. For all the talk of Suitcase Nukes and Dirty Bombs such things are not easy to deliver.
Now avoiding war in the ME is a pretty good Idea. For all the talk and bluster the terrain for a ground war in Iran is such that maneuvers would be a nightmare, and the total land mass is greater than Iraq and Afghanistan combined. To actually contemplate a ground war in Iran one would need to triple the size of the Army and Marine Corps, and even then. . . Deployments might be for the duration, or they might be 18 + months. And the country as a whole would never go for it. These very simple facts leave the political critters wringing their hands thinking that there is nothing they can do.
This is actually not true. I would point to Operation El Dorado Canyon. It wasn't a "massive" strike by any means, it really boiled down to one carrier and a few AF units conducting a few sorties into Libya. But those few sorties literally scared the shit out of Momar. It took Libya from one of the leaders in state sponsored terrorism, down to, well really a country no one really cared about. When we invaded Iraq, Momar was so scared we'd do the same he voluntarily opened up all his WMD programs and disarmed, something the CIA didn't catch.
For too long we've let Iran simmer. There is actually a popular front inside Iran that wants liberalization, and wants western influence. We could easily turn this adversary into a friend. How we do it, is actually rather simple. We strike, hard and without warning, at the sites were nukes are being developed. We strike their military, destroy all their military aircraft (something we can do) and their significant military hardware. Then we make an open plea to the people. We have seen the discontent with the Mullahs. We can use that. The choice is wither we do it or we wait till Israel thinks they have no other options, and they do it. Trust me when I say that would be the worst possible solution.
It appears to me that the choice is Clear. Our Air Force and our Navy can do the job. Maybe not as easily as the civilian public has come to expect, but they can do the job, for now at least. Waiting till this is a full blown crisis, may, in the end be the same as seeing a grenade land in a foxhole and picking up the pretty green ball. Not a good Idea.