Israel’s assassination of Hassan Nasrallah, the long-standing leader of Hezbollah, is a major escalation in its war with the Lebanese militant group.

It has, potentially, brought the region one step closer to a much wider and even more damaging conflict, one that pulls in both Iran and the US.

So where is it likely to go from here?

That largely depends on three basic questions.

Hezbollah is reeling from blow after blow.

Its command structure has been decapitated, with more than a dozen top commanders assassinated. Its communications have been sabotaged with the shocking detonations of its pagers and walkie-talkies, and many of its weapons have been destroyed in air strikes.

The US-based Middle East security analyst Mohammed Al-Basha says: "The loss of Hassan Nasrallah will have significant implications, potentially destabilising the group and altering its political and military strategies in the short term."

But any expectation that this vehemently anti-Israel organisation is going to suddenly give up and seek peace on Israel’s terms is likely to be misplaced.

Hezbollah has already vowed to continue the fight. It still has thousands of fighters, many of them recent veterans of combat in Syria, and they are demanding revenge.

It still has a substantial arsenal of missiles, many of them long-range, precision-guided weapons which can reach Tel Aviv and other cities. There will be pressure within its ranks to use those soon, before they too get destroyed.

But if they do, in a mass attack that overwhelms Israel’s air defences and kills civilians, then Israel’s response is likely to be devastating, wreaking havoc on Lebanon’s infrastructure, or even extending to Iran.

This assassination is as much of a blow to Iran as it is to Hezbollah. It's already announced five days of mourning.

It's also taken emergency precautions, hiding away its leader, Ayatollah Ali Khamanei, in case he too gets assassinated.

Iran has yet to retaliate for the humiliating assassination in July of the Hamas political leader Ismail Haniyeh in a Tehran guesthouse. What has happened now will be causing hardliners in the regime to contemplate some kind of response.

Iran has a whole galaxy of allied heavily-armed militias around the Middle East, the so-called "Axis of Resistance".

As well as Hezbollah, it has the Houthis in Yemen, and numerous groups in Syria and Iraq. Iran could well ask these groups to step up their attacks on both Israel and US bases in the region.

But whatever response Iran chooses, it will likely calibrate it to be just short of triggering a war that it cannot hope to win.

If anyone was in any doubt before this assassination, they won’t be now.

Israel clearly has no intention of pausing its military campaign for the 21-day ceasefire proposed by 12 nations, including its closest ally, the United States.

Its military reckon they have Hezbollah on the back foot now, so it will want to press on with its offensive until the threat of those missiles is removed.

Short of a capitulation by Hezbollah - which is unlikely - it is hard to see how Israel can achieve its war aim of removing the threat of Hezbollah attacks without sending in troops on the ground.

The Israel Defense Forces have released footage of its infantry training close to the border for this very purpose.

But Hezbollah has also spent the last 18 years, since the end of the last war, training to fight the next one. In his final public speech before his death, Nasrallah told his followers that an Israeli incursion into south Lebanon would be, in his words, "a historic opportunity".

For the IDF, going into Lebanon would be relatively easy. But getting out could - like Gaza - take months.