Persistent fighting between Israeli forces and Hezbollah in southern Lebanon is threatening a tentative deal reached between the United States and Iran to end their war.
Their memorandum of understanding includes a ceasefire in Lebanon that would protect Iran’s long-time ally Hezbollah from Israeli strikes, so long as it doesn’t fire at Israel.
The fighting had already led to the postponement of US-Iran talks that would begin the difficult process of resolving long-term issues like Tehran’s nuclear program and sanctions – and the closure of the crucial Strait of Hormuz by Iran’s military brass.
With fighting continuing in southern Lebanon, and looming over resumed negotiations between US and Iranian officials in Switzerland on Sunday, here’s how we got here:
Hezbollah, an Iranian-backed Shiite Islamist movement with one of the most powerful paramilitary forces in the Middle East, has engaged in conflict with Israel for decades, after establishing itself as a force in Lebanon in the 1980s.
It has long been committed to Israel’s destruction and has built up a powerful arsenal of rockets, missiles and drones with Iranian help.
Israel has launched frequent campaigns against Hezbollah, most notably in 2006, when a Hezbollah cross-border raid and the capture of two Israeli soldiers provoked an extensive Israeli air and ground operation that lasted more than a month.
An independent Israeli inquiry described that campaign as “a serious missed opportunity. Israel initiated a long war, which ended without its clear military victory.”
Hezbollah survived, and in October 2023, it began cross-border rocket fire after Israel began bombarding Gaza in response to Hamas’ attack on southern Israel. A year of combat ensued, during which Israel killed Hezbollah’s long-time leader, Hassan Nasrallah.
In November 2024, Israel approved a ceasefire deal that required it to withdraw from southern Lebanon. But Israeli forces continued to hold positions beyond the deadline and carried out near-daily strikes, alleging Hezbollah violations of the deal.
A new cycle of violence began after Israel and the US killed Iran’s supreme leader, Ayatollah Ali Khamenei, in an airstrike in late February.
In early March, Hezbollah began firing at northern Israel in response to its strikes on Iran.
The Israeli military retaliated by launching an intense wave of airstrikes on what it said were Hezbollah positions – and sent troops deeper into Lebanese territory, seeking to establish a buffer zone. It has since emptied most of the south of the country of its residents and demolished thousands of homes in southern Lebanese villages.
The Israeli campaign in Lebanon has killed 4,057 people since March 2, according to the latest figures from Lebanon’s health ministry.
The first paragraph of the 14-point memorandum of understanding shows the end of hostilities in Lebanon as paramount to the agreement.
The agreement stipulates that the US, Iran and their allies “declare the immediate and permanent termination of military operations on all fronts, including in Lebanon, and undertake from now on not to initiate any war or any military operation against each other, and to refrain from the threat or use of force against each other, and ensuring the territorial integrity and sovereignty of Lebanon.”
US President Donald Trump also said Thursday on social media that as part of the deal, “we expect a complete Ceasefire on all fronts, including Lebanon, Hezbollah, and Israel.”
For Tehran, an end to Israeli attacks on its most significant ally in the region has always been a central demand amid the torturous negotiations to end the three-month old conflict.
On Friday, a diplomat with knowledge of the matter told CNN that Iran asked for guarantees that hostilities in Lebanon will end before it resumed talks with the US. Those fraught discussions – mediated by Pakistani and Qatari officials – began again on Sunday.
For the Israeli government, not having the freedom of action to further degrade Hezbollah is anathema – and a serious test of its close alliance with the United States.
“With all due respect to the Americans, Israel must make it clear to the entire world that the blood of our sons and the security of our citizens are not up for sacrifice,” Israel’s far-right National Security Minister Itamar Ben Gvir said Friday.
Israeli Prime Minister Benjamin Netanyahu has repeatedly said Israel will not withdraw from Lebanon.
“We will restore security to the north (of Israel),” he said on Thursday in his first public remarks since the text of the US-Iran agreement was published. “This requires maintaining the security zone in southern Lebanon, and it requires that we not leave it as long as Israel’s security needs demand it.”
Hezbollah denied Israeli claims that it had violated the ceasefire, accusing Israel of continuing the war despite the US-Iran agreement and saying the group “will remain vigilant against any aggression.”
On the Iranian side, deep mistrust in the US and its ability to finalize a deal continues to cast a shadow over negotiations.
“The United States’ failure to abide by the first clause of the memorandum of understanding shows that America still lacks the will to gain the trust of the Iranian people,” Ebrahim Azizi, chairman of the Iranian parliament’s national security committee, said on Saturday.
Both President Trump and Vice President JD Vance have shown growing impatience with Israel’s strikes in Lebanon this month and its hostility to the Iran memorandum.
“If I was in the cabinet of the Israeli government, I might not be attacking the only powerful ally that I have anywhere left in the entire world,” Vance said this week.
Trita Parsi, the executive vice president of the Quincy Institute for Responsible Statecraft, said that “Vance is not changing the conversation about Israel in the US. He is changing the entire paradigm.”
Israel still has many supporters in Washington, especially in Congress, and Trump said Friday – despite some bruising conversations with Netanyahu – that “we fought very well with Israel, and we’ve had a great relationship with Israel.”
The answer may depend on how far Trump is willing to go in enforcing the ceasefire without having Netanyahu fully onboard.
“The principal spoiler of any broader understanding with Iran remains Lebanon,” wrote Danny Citrinowitz, former head of the Iran branch of Israel’s military intelligence, adding that “the central question is how far the United States is prepared to go in enforcing a ceasefire that both sides interpret differently.”
In talks with the Lebanese government, Israel has persistently demanded it disarm Hezbollah – but so far the Lebanese military has been unable to do so.
“The main political victim of the war in Lebanon appears to be the Lebanese government, which is sidelined in the talks about a ceasefire and thus undermined by the US, Iran, Israel and Hezbollah,” wrote Emile Hokayem at the International Institute for Strategic Studies.
“Nothing surprising but immensely problematic and with long-lasting implications. Iran has succeeded in linking Lebanon and Hormuz and Israel’s foolish military-only strategy has backfired,” Hokayem wrote on X.
