After Israel's 'preemptive' strike on Hezbollah targets, what happens ...

The Middle East is now at the most dangerous point it has reached for many years.

Today, the Israeli military launched air strikes at targets in southern Lebanon, describing them as a pre-emptive action against Hezbollah. 

The world's most armed militant group later appeared to confirm the plan, saying it had launched hundreds of rockets at Israel. 

The extent of damage on either side isn't immediately clear.

Since the Hamas-led attack on Israel on October 7, Israel and the Lebanese-based Hezbollah group have been exchanging fire.

It's been at a relatively low level, with neither side pulling the trigger on a big regional war.

Both sides know that such a development could be mutually devastating.

The last time Israel and Hezbollah went to war was in 2006, when everyone suffered and neither side won.

In fact, Israel's official inquiry into the conflict, the Winograd Commission, found they had been badly prepared for the war and executed it badly.

Hezbollah is an infinitely more formidable enemy than Hamas. 

The fact that after 10 months of war in Gaza, Israel is still struggling to defeat Hamas shows that such battles are never easy.

Hamas leader Yahya Sinwar still cannot be found, even in an area as small as Gaza.

Hamas is still able to fire missiles from Gaza into Israel.

And despite Israel's military and technological superiority, defeating Hamas is proving difficult. 

Israeli military planners know that trying to defeat Hezbollah would be much more difficult. 

Credible sources suggest that Hezbollah has as many as 150,000 missiles hidden in the mountains of southern Lebanon, south of the Litani river.

Displaced Lebanese beg to go home as country braces for war

People from southern Lebanon have had to flee the daily air strikes on their villages, and for months have stayed in derelict hotels-turned-shelters.

The significance of the missile arsenal is that it could overwhelm Israel's Iron Dome anti-missile system, no matter how state-of-the-art that system is.

As Zohar Palti, an ex head of intelligence at Israel's intelligence agency, Mossad, told the ABC for tomorrow's Four Corners, should Hezbollah activate such a war, Israel would then reduce Beirut to "a football court". 

The world has watched during the past 10 months as Gaza has been rendered largely unliveable.

Many in the region fear that should war break out in Lebanon, Israel may also engage in saturation bombing of Beirut.

What happens now? 

There are two key reasons Hezbollah is more formidable than Hamas.

Firstly, it has an unimpeded supply of weapons from Iran. 

Hezbollah controls the airport in Beirut, so plane-loads of weapons are able to be brought into Lebanon's capital, then taken to the country's south, near the border with Israel.

Secondly, Hezbollah's troops are better trained and resourced than those of Hamas. 

Hezbollah fighters spent several years in neighbouring Syria where they helped to prop up the regime of Bashar al-Assad, fighting and usually defeating Sunni militia groups, which were part of the attempt to dislodge the government. 

The key to what happens now is Iran's Supreme Leader, Ayatollah Ali Khamenei.

This 85-year-old cleric runs Iran. 

He has full control over his country's Revolutionary Guard, the security and military machine that keeps him in place.

Right now, the Revolutionary Guard will be advising Ayatollah Ali Khamenei on what should happen next.

The Iranian Revolutionary Guard has long been preparing for a war with Israel, just as Israel has long been preparing for the same event.

Should the "Big War" occur — as many in Lebanon and Israel refer to a regional conflict — casualties on both sides will be high.

Two global assassination plots in 24 hours

Specifics about how Hamas political leader Ismail Haniyeh and Hezbollah commander Fuad Shukr were killed on Tuesday are scarce, but one thing is certain: the two high-profile hits will further destabilise the Middle East.

Iran is likely to be careful not to directly hit Israel, preferring to do so via its proxy, Hezbollah.

In turn, Iran's proxies in Syria and Iraq — Shia Muslim militia groups — may escalate their previously sporadic attacks on US defence facilities through the Middle East.

After this new increase in hostilities, Hezbollah said it had completed its "first phase."

Should Iran's Supreme Leader decide that the next phase is to activate those 150,000 missiles, a regional war will have begun.