Israel’s strike on Hezbollah leader is an alarming escalation in conflict

Israel’s claimed assassination of Hezbollah’s leader, Sayyed Hassan Nasrallah, in a massive strike on an underground headquarters in Beirut’s southern suburbs marks the most alarming escalation in almost a year of war between the Shia militant organisation and Israel.

Immediately after a bellicose speech by the Israeli prime minister, Benjamin Netanyahu, at the UN general assembly – where he appeared to directly threaten Iran as well as promise to continue “degrading” Hezbollah – the first reports of a major strike began to emerge.

In less than an hour, Israeli journalists with connections to the country’s defence and security establishment were suggesting Nasrallah was the target and that he had been in the area of the headquarters at the time of the strike. On Saturday morning, the Israeli military said he had been killed.

That the strike was regarded as highly significant was quickly confirmed soon after it happened by a series of statements from Israel – including an image showing Netanyahu ordering the attack on the phone from his New York hotel room.

Related: What is Hezbollah’s role and influence in Lebanon?

What is clearer than ever, after a series of Israeli escalations against Hezbollah this month – including targeted killings and the explosion of thousands of modified pagers and walkie-talkies supplied to the group – is that the long-understood ground rules governing the balance of deterrence between the two sides has been blown away.

For much of the early months of the conflict with Hezbollah, which began on 8 October – a day after Hamas’s attack from Gaza – it was understood Israel would not assassinate the militant group’s most senior members. But in recent months those “red lines” have increasingly been rubbed away.

As the geographic scope of attacks on both sides has moved deeper into Lebanon and Israel, so Israeli operations have aimed at ever more senior Hezbollah commanders, beyond those directly involved in launching strikes on the ground in Lebanon’s south.

Indeed, since the beginning of the year, diplomats and knowledgeable analysts in the region have suggested that one aim of the discreet to-and-fro between Israel and Hezbollah through US special envoy Amos Hochstein and intermediaries for the group has focused on preserving the understanding that the most senior figures in the militant group would not be targeted.

On the Israeli side in the past fortnight, however, evidence has been building that a case was being made for a significant escalation.

Claims of unsuccessful Hezbollah plots aimed at senior Israeli figures were made by the country’s security agencies, while it was also suggested that the Israeli escalation was aimed at countering the militant group’s own plans to launch a large offensive.

All of which, it now seems clear, was a preamble for a long-prepared and multi-pronged effort to decapitate Hezbollah.

While it may take several days to understand the full import of the fallout from Friday’s strike, Netanyahu and his military chiefs have taken an enormous gamble, not simply regarding the situation in Israel’s north, where tens of thousands have been displaced by the fighting, but with the wider region and with the country’s relationships with its international partners.

Coming in the midst of US- and French-led international efforts to broker a three-week ceasefire with Hezbollah, the move marks an emphatic slap in the face for the Biden administration, which believed it had an assurance from Netanyahu that he backed the temporary truce.

Related: ‘We are winning’: Benjamin Netanyahu defies calls for ceasefire in UN speech

Instead, it appears that Netanyahu and his military leadership were all the time secretly laying the ground for an attack timed to violently underline the rhetorical flourishes of the Israeli prime minister’s warnings to Hezbollah and Iran during his thinly attended speech on Friday at the UN.

Most significantly, the strikes represent a direct challenge to Tehran, for whom Nasrallah represented its most important strategic regional ally, whose tens of thousands of Iranian-supplied missiles aimed at Israel have long been seen as a key strategic foil preventing an Israeli attack on Iran itself.

Now all bets are off. Despite anonymous Israeli claims – later disavowed by the IDF – that it had destroyed up to 50% of Hezbollah’s missile arsenal of well over 100,000, that remains highly unlikely. And while Hezbollah’s command and control has been severely damaged, it is probable that it retains a significant capacity.

Other Iranian allies, including in Iraq, Syria and Yemen, have their own missiles and drones, which, while not as significant as Hezbollah’s, could be brought into play – and not necessarily only against Israel but against US targets.

Then there is the most important question: whether Iran can accept the strike against Nasrallah, or whether it too could be drawn into a widening conflict, and whether the strike is intended by Israel as setting the conditions for a strike against Iran.

Underlying that concern, Iran’s embassy in Beirut condemned Israel’s airstrike, saying on Friday night – before Israel’s claim that Nasrallah had been killed – that the attacks “represent a serious escalation that changes the rules of the game”, and that Israel would be “punished appropriately”.