The killing of Saleh al-Arouri, one of Hamas' most senior leaders, marks a new phase in the war between Israel and Hamas. The key question now is: what will Iran do?
The fight against Hamas has been taken into the heart of Lebanon, which hosts Hezbollah, the Shia militant group that takes no major military decisions without the approval of Tehran.
Al-Arouri was Hamas' number two political leader — he reported to Ismail Haniyeh, the head of Hamas based in Qatar.
While al-Arouri was a member of Hamas, not Hezbollah, the latter will be affronted because it believes Israel has committed this assassination by coming into Hezbollah territory — the southern suburbs of Beirut.
Israel has not officially claimed the killing. With this sort of assassination, it never does. But the reaction of political leaders in Israel, the delight in the killing, implies that if Israel did not carry out the assassination, then it wished that it had.
"Whoever did this strike was very surgical and went for a Hamas target because Israel is at war ... whoever did this has a gripe with Hamas," Mark Regev, a senior advisor to Israeli Prime Minister Benjamin Netanyahu, told MSNBC.
Lebanese and Palestinian security officials are also convinced that Israel orchestrated the killing — and it certainly fits with previous targeted killings carried out by Israel.
Israel has made clear since Hamas' October 7 massacre that it will hunt down Hamas commanders and kill them wherever and whenever it gets the chance.
Because it happened in Hezbollah territory, the instincts of many in Hezbollah will be to dramatically escalate the rocket attacks which have been occurring sporadically from Lebanon into Israel since October 7.
Loading...No appetite for a new war
Neither Israel nor Hezbollah wants a new war. The two were at war between 1982 and 2000 when Israel withdrew from its almost 20-year occupation of Southern Lebanon. If Israel or Hezbollah wanted a new war, both could have triggered it by now.
Israel far prefers to carry out this sort of targeted killing than a full-scale war with Hezbollah. Hezbollah is a much stronger military opponent than Hamas.
While Hamas has shown itself to be better armed than Israel realised it was, Hamas is not able to access weapons on the scale that Hezbollah is.
Hamas is blockaded on three sides by Israel (the fourth by Egypt). While it's clear this has not stopped weapons getting into Gaza, or being manufactured in the enclave, for Hezbollah there are no restrictions on weapons.
Hezbollah controls the airport in Beirut, which means planes with missiles and other weapons can (and do) arrive from Iran.
The group is believed to have as many as 150,000 missiles stationed in southern Lebanon — all ready to be fired into Israel should Tehran give the signal.
Israel preparing for war with Hezbollah
While not wanting a new war, Israel is prepared for a war with Hezbollah if it needs to have one.
But it would rather focus on eliminating Hamas, once and for all, as any sort of military threat. While it has already degraded much of Hamas' capability by its air, sea and ground attacks since October 7, Hamas is still operating.
That is evidenced by two things. Firstly, Hamas is still able to fire rockets into Israel, even if most of them are intercepted by Israel's Iron Dome anti-missile system.
And secondly, as long as Hamas' commander in Gaza, Yahya Sinwar, has not been captured or killed, then Israel will want to focus on Gaza.
Loading...From Hezbollah's point of view, Lebanon is already in a desperate situation. The economy is an appalling condition, something which has been exacerbated in recent years by the war in Syria.
Lebanon is now trying to support a huge number of refugees from Syria. According to Human Rights Watch, Lebanon hosts more than an estimated 1.5 million refugees who fled Syria since 2011, making it the country with the largest number of refugees per capita in the world.
Hezbollah will also be considering another factor: it knows that should it engage in a full-scale war with Israel, parts of Beirut — particularly the southern suburbs — could end up looking like large parts of Gaza. Rubble. Memories of Israel's 2006 bombardment of Beirut are still fresh.
The two key political dynamics will be whether Hezbollah wants to take the pain that a war with Israel will bring and whether the leaders of Iran take that into consideration or are prepared to sacrifice the wellbeing of the Lebanese people to further their own hatred of Israel.