Are you suggesting that the war in Iraq has been a disincentive for Iran's nuclear weapons program?
I'm stating that the current situation in Iraq is irrelevant to the Iranian nuclear program ie neither an incentive nor a disincentive.
Pakistan, who are Sunni Muslims. Their program was also closely linked with Saudi Arabia, who are also Sunni Muslims, and are currently armed with Pakistani nuclear-capable ballistic missiles.
What message does this transmit to Iran? That if they have nuclear weapons they'll be invaded?
Not at all. Your arguments linchpin is that North Korea hasn't been invaded because it has nuclear weapons. It ignores the fact that the US didn't invade North Korea when they didn't have nuclear weapons, while it did invade Iraq when Iraq didn't have nuclear weapons. This suggests that nuclear weapons possession is irrelevant to being invaded by the US.
Your argument also overlooks the fact that the Iranian nuclear program was started long before the US invaded Iraq.
Are you suggesting that the destructive capacity of a hydrogen bomb is equivalent to that of a mustard or sarin gas shell?
No, I'm suggesting that the escalation path is non-linear. The use of any WMD is considered to be provocation for use of all other WMD. Using chemical weapons on US forces for example, is considered to be sufficient provocation for nuclear retaliation.
In fact, if I recollect correctly, the U.S. currently possesses conventional weapons that have the potential to be more destructive than a lot of chemical weapons.
Such as?
We can start with the issue of nuclear fallout.
Nuclear fallout is a short-lived problem ie less than a month. All of the really nasty products have decayed by then. The products with long half-lives aren't a problem, because the reason they have long half-lives is that they're not terribly radioactive.
Persistent chemical weapons OTOH will kill for years. VX in particular is extremely difficult to decontaminate.
Nuclear weapons have next to no practical utility.
To a nation lead by rational people, they lead to strategic paralysis. To a nation lead by religious fanatics, surrounded by what they view as heretics? Maybe they'd see it differently.
Kevin