As appealing as your suggestion is, it probably wouldn’t work.
With a nuke, it’s clean, easy to target, and if fired from a boomer at sufficient distance, there’s no way to retaliate since the launching sub could ‘shoot & scoot’. Besides, there are three or four nations that the world KNOWS has a sub-based nuke capability. So unless you actually SAW the missile when it launched to ID the country that built or launched it, you really don’t know who did, so who could you blame? Not only that, but you’ll have NO chance of shooting down the incoming RV and NO chance of evacuating the city.
(I know...there EXISTS a capability to possibly terminate an inbound warhead, but there’s only TWO countries I know of who have that capability: US and Israel. Ergo, the Kingdom is SOL.)
The problem with conventional bombing is that you’d have to launch a rather LARGE bomber force to adequately destroy the city, not to mention the Grand Mosque itself. What do you think the Kingdom’s response is going to be when their radar spots a massive bomber force headed their way? They’ll launch every F-15 (which WE sold them) they have to intercept. A potentially large loss of our forces could occur. Also, there would be time to evacuate at least the central area of Mecca before the bomber force arrived.
Nice analysis. Academically speaking though, I like the idea of a suitcase nuke. Far more delicate of an operation, indeed, but more potential for obfuscation of blame.
But, I do understand that the first country to get caught using a nuke will be the focus of all. For instance, the consequence of Iran using a nuke on Israel will be short-sighted. Even the Kingdom will be obliged to attack Iran if for no other reason then survival (sunni-shia thing, IIRC).
If the USA were to go that route, we might as well drop half the arsenal on many targets. God, I hope we never come to that unless there is the second coming.