The large number of 'Hezbollah' rockets/missiles are a grave danger that is specific to Israel. In the Second Lebanon War (which Israel lost), the 'Hezbollah' forces were simply demonstrating their ability to 'deliver ordinance-on-target' over northern Israel using mostly relatively short range unguided rockets and 'dumb' warheads (simple high explosive warheads). Like Saddam Hussein did in the first Gulf War with his Scuds (actually al-Hussein missiles; a modified version of the Scud), the Iranians and Syrians using their Hezbollah proxies, were delivering a warning by firing repeatedly into their enemy. They were demonstrating their ability to hit their enemy but were only, by choice, using low impact 'dumb' high explosive warheads. Saddam held back a force (19 or more) of missiles armed with WMD, which is why we did not 'finish' the war the first time. (It was only after he had denuded himself of his WMD and delivery capabilities that we began the Iraqi War - Second Gulf War).
The Iranians and Syrians and their Hezbollah allies/proxies have a considerable selection of WMD available for these 40,000 to 60,000 rockets/missiles (in addition to their Syrian and Iranian based longer range missiles). The WMD can range from FAE (fuel air explosive) warheads (which if fired in a coordinated pattern can lay down a FAE 'brew' over a wide area, such as over a heavily populated urban area) and achieve PSI (pounds per square inch) levels higher than standard NATO tactical nuclear warheads. The WMD can also include chemical warheads of various types. Syria and Iran have one of the largest (if not the largest) joint chemical warfare programs on Earth. Additionally, they can use Advanced Biologically produced biotoxin warheads for a longer lasting chemical war 'effect'. They can also use 'dirty bombs', that is Radiological warheads using things like Cobalt 60 and Strontium 90, which give the 'effect' of radiological fallout without using a nuclear blast. They can also use Radiological weapons encased in an advanced matrix containing hard to remove glue, so that the radioactive particles are glued to buildings, cars, etc., making any decontamination efforts most difficult.
The Israelis see these rockets/missiles and their assorted warheads as a grave threat. The Second Lebanon War was planned as the first step in a war against Syria and Iran but the low-cost but powerful AT-14 Russian built and supplied anti-tank missiles proved too much for the IDF armor; the losses were simply too high. This time the IDF will be using different tactics, strategies, and weapons.
Both Syria and Lebanon have make it very clear, over the last few months, that any large-scale Israeli attack on Lebanon/Hezbollah will be considered an attack on them and will immediately trigger a regional war with themselves and Israel. They simply cannot allow Israel to destroy the rocket/missile element to their MAD counter-force, as they know that the Syrian and Iranian homelands would be next. So any war on Lebanon/Hezbollah means a General Middle East War from day one.
Any Third Lebanon War/General Middle East War is apt to involve WMD on both side quickly as both sides know the stakes and that the Israelis are determined to end, once and for all, any Iranian opposition to a 'Greater Israel' domination of the entire Middle East. It will be a case of 'use your WMD or lose them' to enemy strikes. Any massive WMD usage against Israel will result in the usage of Israeli thermonuclear warheads against Arab and Persian populations centers in large parts of the Middle East, with the resulting spread of radioactive fallout over large parts of the Northern Hemisphere. However, the first use of nukes is apt to be lower yield warheads directed against Iranian underground facilities including both nuclear sites and governmental command and control and leadership bunkers, with some limited strikes also likely early-on in Syrian territory.
The Iranians are well prepared to launch a global Advanced Biological Warfare terrorism based strike against not only Israel and American and allied forces in the Middle East but also against the American, Canadian, British, French, German, Italian, etc., homelands. This will utilize DNA recombination based genetically engineered 'super killer viruses' that are designed to spread themselves throughout the world using humans as vectors. There are very few defenses against such warfare, other than total quarantine of the population until all of the different man-made viruses (and there could be dozens or even over a hundred different viruses released at the same time) have 'burned themselves out'. This could kill a third of the world's total population.
Such a result from an Israeli triggered war would almost certainly cause a Russian-Chinese response that would eventually finish off what is left of Israel and begin a truly global war/WWIII with multiple war theaters around the world. It is highly unlikely that a Third World War, fought with 21st Century weaponry will be anything but the Biblical Armageddon.
The entire World is facing a danger that is much worst than what it faced in the Cuban Missile Crisis of the early 1960s, which came close to going nuclear. At the present time, the AIPAC controlled political class in America is unwilling and seemly unable to mount any opposition to the Israeli drive towards war. This will be a fatal shortcoming that future historians will write about someday, assuming anyone is left to write about it.