Before any Israeli and/or American strike on Iran there will first be an attack on the well dug in Hezbollah Special Forces in Lebanon. This is because the Hezbollah rocket forces there are a strategic threat to Israel's existence and a strategic checkmate by Iran and Syria against Israel's nuclear arsenal. In fact the 2006 Lebanon War (known in Lebanon as the "July War" and in Israel as the "Second Lebanon War") was a failed attempt to neutralize the Hezbollah threat.
The Hezbollah Special Forces are in-effect a highly trained and well-equipped Iranian commando force of at least a Brigade in size. They man and protect a large number of mostly unguided and rather crude rockets, generally Katyusha 122mm artillery rockets with a 19 mile/30km range and capable of delivering approximately 66 pounds/30kg of warheads. Additionally, Hezbollah are known to possess a considerable number of more advanced and longer range missiles. During the 2006 war Hezbollah fired approximately 4,000 rockets (95% of which were Katyshas) all utilizing only "dumb" high explosive warheads. Some Iranian build and supplied Fajr-3 and Ra'ad 1 liquid-fueled missiles were also fired. At the time of the 2006 war Hezbollah was reported to have in the range of 13,000 rockets. There are creditable reports that this number has been rebuilt and expanded upon since the end of that war.
During the 2006 war the world watched as Israeli towns were hit time and time again by the Katyushas. What was not discussed by the main stream news media was the fact that the ordinance delivered by the Katyushas was mainly harassment fire with very limited effect. The Iranian/Syrian trained and supplied Hezhollah commandos were holding back their "heavy stuff" both in terms of their longer range guided missiles capable of hitting southern Israel and most importantly warheads of strategic military importance. That is NBC (nuclear [in this case radiological] chemical and biological) and advanced-conventional warheads. They were demonstrating their ability to deliver "ordinance on target" and their ability to survive a heavy Israeli ground and air combined arms attack.
Hezhollah has the capability of loading truly strategic warheads on the large number of mostly crude older technology unguided rockets that it has. The use of advanced-conventional fuel-air explosive (FAE) warheads on the Katyushas would have had a much more profound effect in Israeli cities. The use of FAE submunitions on the larger missiles capable of hitting any target in Israel would have given Hezhollah the firepower of low-yield nuclear weapons without crossing the nuclear threshold. Coupled with the large number of missiles in Syria and those in Iran, the Hezhollah rockets posed, and continue to pose, a truly grave strategic threat to Israel if FAE warheads are used. This threat is dramatically increased if radiological ("dirty bombs"), chemical, and/or biological warheads are used.
FAE warheads work somewhat like a automotive engine's carburetor. They mix fuel with a much larger amount of air to create an explosion, which in the case of the car drives the camshaft but in the case of a FAE creates a rather large footprint bomb. Instead of a bomb the size of your living room sofa (like a 1,000 bomb), the fuel air vapor cloud, created by the FAE aerosol, can create a bomb the size of a city block (or even much larger if multiple guided missiles with FAE submunitions are used). FAEs use an embedded detonator to trigger the fuel air "brew" which itself results in a high overpressure blast followed by a vacuum effect. In fact the Russians refer to FAEs as "vacuum bombs". An exposed person would likely be killed by the overpressure but in any case, should a person survive the overpressure blast the vacuum effect has been known to suck the lungs right out of people. FAEs can utilize a number of liquid explosive bases, including gasoline. A gasoline FAE uses a ratio of gasoline fuel vapor to air at a 1.3% to 6% gasoline to 98.7% to 94% air mix. The FAE can be spiked with assorted agents, such as powered aluminum, to increase blast effect. The Russians have developed variations of the FAE such as a slurry-explosive warhead (a mix of a combustible liquid with solid high explosives) and a reactive-surround warhead (nitrocellulose and combustible aluminum in a thin walled container).
The massive number of Hezbollah rockets could also be outfitted with chemical warheads. It is worth noting that the joint Syrian-Iranian chemical warfare R&D and production program is perhaps the largest and most complicated on earth. Generally the Israelis have shown themselves to be prepared for chemical warfare, however a chemical war attack following closely behind a FAE attack (to open up bunkers and apartment buildings) would greater effect. While it is not necessary to utilize a rocket to deliver a biological war attack, it could be done and there is some benefit militarily to a rapid dispersal of biowar agents under the cover of conventional attacks. Radiological weapons deliver the long term (which can be hundreds of thousands of years) lethal effects of radiation without the blast effect of a nuclear bomb.
In the 2006 war, this was attempted by Lt.-General Dan Halutz, the Israeli Air Force general who was the Chief of Staff of the Israel Defense Force, and Prime Minister Ehud Olmert. They seriously miscalculated. The Syrians had bought a large number of very nasty, relatively low cost Russian AT-14 Kornet solid fuel anti-tank guided missiles (ATGM) and the Iranian trained Hezbollah commandos dug in massive numbers of concrete bunkers and firing positions. After over 50 Merkava main battle tanks were hit, and the high tech American made warplanes and pinpoint weapons proved ineffective, the handwriting was on the wall. Either use neutron bombs or lose a large number of Israeli solders to remove the Hezbollah threat; or declare peace and walk away for the time being ~ the Israelis chose the latter.
Since the Israelis do not like being caught with their pants down, they have been spending a considerable amount of time seeking a non-nuclear military solution to the Hezbollah threat. I suspect that the solution will utilize massive numbers of FAEs. Then we shall see if the Iranian combat engineers have build the bunkers to withstand the vapors of massive numbers of FAEs (this means air tight bunkers that are very strong). The real danger point will come if either, a second non-nuclear Israeli attempt fails, or if it appears to be succeeding. If it fails, the temptation to use neutron bombs will be very high on the Israeli side. If it appears to be succeeding, the Hezbollah side (with their Iranian and Syrian backers) will be faced with the "use it or lose it" option for their strategic rocket force. Using the full force of the massive number of rockets with strategic weapons on the Israeli population would ensure a full nuclear response from the Israel Defense Force. Not using the strategic weapons would mean that a massive US/Israeli/allied attack on Iran (and perhaps Syria) would be highly likely, and the destruction of Iraq and its leadership has shown the high stakes involved.
I am reminded of an old Chinese curse, "May you live in interesting times". It appears that the year 2008 may be among the most interesting of times (especially in light of the Iranian global ability to use advanced biological war against its enemies).