The Israelis have considered Iran to be their primary threat ever since the end of the first Gulf War. Since that time, the Iraqis have had no real weaponry to pose a serious threat to Israel. Iran then emerged as Israel's primary concern - it was known as early as 1992 that the Iranians had embarked on a long-term, measured program to acquire nuclear technology, followed by the establishment of a nuclear weapons program.
Although neighboring Syria has chemical weapons and the ballistic missiles to deliver them, Israel does not consider it likely that Syria would launch an attack on Israel. They (and I) believe that the Syrians regard their chemical warhead equipped missiles as a counterbalance to the Israeli nuclear threat. (It also gives the Turks, Jordanians and Iraqis something to think about.) I think the Syrians realize that a first strike on Israel using chemical weapons would elicit what I call a "Biblical, Old Testament" response. When the Defense Department did the computer modeling in 1990, we determined that a Sarin warhead detonated in an air burst at 1,000 feet over Tel Aviv could, in perfect conditions, kill as many as 8,000 people.
The Iranian Shihab-3 and -4 series of missiles are derivations of North Korean Nodong missiles. Neither of them are useful to carry conventional warheads, as they are inaccurate that hitting a target at range would be problematic - sort of like the Iraqi modified Scuds (Al-Husayn, Al-Hijarah, Al-'Abbas). Therefore, one must assume that Iran is developing a WMD-type warhead.
Would the Iranians use a nuclear weapon against Israel just because they could? I doubt it - but if someone else in the region has them, the prevailing wisdom is that you better get them too. It is the old Mutual Assured Destruction, Cold War theory. Going one better, if that fails, the anti-ballistic missile capability is the fall back, possibly even the only guarantor of your national survival.
I won't get into the technology involved; eventually, it will be feasible.
Personally, I tend to think the existence of a credible ABM system in the hands of the Israelis might be destabilizing. If I had nuclear weapons, ballistic missiles, a long-range capable air force, and possibly in the near future a credible ABM capability, I would be tempted to take out the Iranian program, just as the Israelis did to the Iraqi program in 1981. I assess that Israel has all of the required capability, and has demonstrated the political will to use their long range strike capability to attack targets as far away as Iraq and Tunisia.
This will be the 12th test of the Arrow. Although planned over three years ago, it comes at a time when Israel is renewing its warning of Iran's nuclear possessions and intentions.I assess Israel's warning as one that could be backed up if; the Iranian threat cannot (at least at this time). Statements like the Iranian threat might push Israel into action. Also, factor in to their thinking the fact that Iran is the major supporter of Hizballah in Lebanon, as well as Hamas and the Islamic Jihad in the Occupied Territories. If you lived in Tel Aviv, would you want Tehran to have nuclear weapons?
On Tuesday, the Islamic Republic vowed to "wipe Israel off the earth" if any strike is made against their nuclear installations.