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Israel has launched a ground operation across its northern border into Lebanon targeting the Iran-backed militant group Hezbollah, opening a new and dangerous phase in almost a year of war.

The incursion, which Israel’s National Security Cabinet has called the “next phase” of its war with Hezbollah, marks the fourth time that Israeli soldiers have publicly entered Lebanese soil in nearly 50 years, and the first since Israel’s 34-day war in the country in 2006.

Israeli troops laid the groundwork for what it called a “limited ground operation” in recent days, ramping up airstrikes that have killed hundreds of people, destroyed homes and displaced about 1 million people in Lebanon.

The latest escalation comes after Israel killed Hezbollah’s leader Hassan Nasrallah in an airstrike on Friday and decimated the leadership of the most powerful paramilitary force in the Middle East.

Here’s what we know.

Extent of incursion unclear

Israeli officials have characterized the incursion into southern Lebanon as limited in scope, saying there will be “no long-term occupation.”

Officials have, however, declined to say how deep Israeli troops would venture into the country or how long the operation is expected to last. On Tuesday, the Israeli military called on residents in more than two dozen villages in southern Lebanon to evacuate approximately 30 miles into the country.

An Israeli security official told reporters on condition of anonymity Tuesday morning that the operation does not amount to an invasion or incursion, describing it instead as “localized raids” that are “very limited in scope and in the area of operation.”

The official said there were so far “no clashes” on the ground between the IDF and Hezbollah, but refused to comment on whether Israeli tanks have entered Lebanon and would not elaborate on how deep into Lebanese territory Israeli troops have advanced, saying they were focused on the border areas.

“The amount of forces and the type of forces are more appropriate to something of a limited raid, and not, for example, things we’ve seen in Gaza with very, very large forces,” the official added.

Hezbollah rejected the claim that Israeli forces had entered southern Lebanon, describing them as “lies,” according to a statement by spokesman Mohamed Afif on Tuesday.

A source from the UN Interim Forces in Lebanon (UNIFIL) said the Israeli military has staged some “sporadic raids” across the Lebanon-Israel border but its troops have not remained on Lebanese soil. The assessment that Israel has not yet launched a full-scale invasion was supported by two other high-level Lebanese security sources.

Hassan Ammar/AP
A man stands on the rubble of buildings near the site of the assassination of Hezbollah leader Hassan Nasrallah in Beirut's southern suburbs, on September 29, 2024.

The Israeli military earlier said it was focused on removing “immediate threats” from Lebanese villages along the border, including Hezbollah’s ability to infiltrate northern Israel. Israeli soldiers, including paratroopers and commandos, as well as armored corps troops have been “preparing for limited, localized, targeted operations in southern Lebanon,” the Israeli military said, adding that soldiers have been training for weeks and had gained skills and operational experience in Gaza over many months.

While the extent of Israel’s military plans inside Lebanon remain unclear, Prime Minister Benjamin Netanyahu has become increasingly defiant of international calls for restraint and de-escalation, as well as widespread outrage over growing civilian casualties in Lebanon and Gaza.

Previous military operations initially declared by Israel to be limited in their goals have proved to be anything but.

Examples include Israel’s years-long occupation of southern Lebanon that began in 1982 with the stated aim of a brief and limited mission to destroy the Palestinian Liberation Organization (PLO) in the country.

More recently, Israel’s military declared a “limited” operation in Rafah, southern Gaza that has left the city in ruins.

What happened ahead of the incursion?

Shortly before the incursion, Israel’s National Security Cabinet approved the “next phase” of its war with Hezbollah, according to Israeli media.

In preparation, the Israeli military launched small raids and artillery fire across the Lebanon border, and sealed off several communities in northern Israel, limiting the movement of civilians there.

The Lebanese army had also evacuated observation posts at the southern border and moved to barracks in the border villages, according to a Lebanese security source. The Army Command later denied reports it withdrew. CNN is unable to independently verify the Lebanese army’s movements.

Meanwhile, Israel’s air force once again bombed the southern suburbs of the Lebanese capital Beirut, predominantly Shia neighborhoods where Hezbollah has a stronghold.

It follows Israeli airstrikes that hit inside Beirut’s city limits early Monday for the first time since the Palestinian militant group Hamas’ October 7 attacks on Israel.

The Lebanese health ministry said on Monday that at least 95 people have been killed in Israeli strikes in just 24 hours, and another 172 others injured.

Kawnat Haju/AFP/Getty Images
Smoke billows after an Israeli strike on a village near the southern Lebanese city of Tyre on September 29, 2024.

Isn’t Israel fighting Hamas in Gaza? Why are Israeli troops now in Lebanon?

Israel and Lebanon-based Hezbollah have been engaged in a tit-for-tat escalation since the war in Gaza began following Hamas’ attack on Israel last October. Hezbollah first attacked Israel on October 8 and has said it will not stop striking Israel until a ceasefire is reached in the Palestinian enclave, much of which has been reduced to rubble by Israeli bombs and fighting.

In recent weeks, Israel has refocused its military objectives north with a new war aim to return displaced residents to their homes along the Lebanon border. About 60,000 Israeli civilians have been forced from their homes by Hezbollah’s rocket attacks.

What’s unfolded is some of the fiercest fighting between the two longtime foes since the 2006 Lebanon war, which killed 1,100 in the country. Nearly 50 Israeli civilians and 121 Israeli soldiers were also killed.

Last month, pagers and walkie-talkies used by Hezbollah members exploded across Lebanon in a coordinated Israeli attack that killed dozens of people and maimed thousands, including women and children.

Israel has also stepped up a relentless bombing campaign across Lebanon targeting Hezbollah’s infrastructure and leadership, but the strikes have also decimated homes and neighborhoods in densely populated areas. Massive airstrikes in southern Beirut have killed a string of Hezbollah leaders, as well as more than 1,000 people.

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The Iran question

The latest developments raise questions about how a weakened Hezbollah will respond, and the extent to which its backer Iran could get involved, once more ratcheting up fears of a wider regional war.

Hezbollah is part of an Iran-led alliance spanning Yemen, Syria, Gaza and Iraq that has attacked Israel and its allies since the war with Hamas began.

In a fiery speech on Sunday, Netanyahu said one of Israel’s goals is “changing the balance of power in the region” and that “there is no place in Iran or the Middle East that the long arm of Israel will not reach.”

Killing Hezbollah leader Nasrallah and wiping out the group’s capabilities to launch a large-scale attack on Israel were “necessary” conditions to achieve that goal, he said.

Israel has also ramped up attacks on multiple fronts against other Iran-backed militants, including launching strikes targeting the Houthis in Yemen.

But despite the recent Israeli strikes on its proxies, Iran has appeared wary of moving into direct conflict with its longtime enemy, even as their decades-long shadow war has been pushed further into the open. Many observers fear any direct Iranian retaliation could draw the United States further into the conflict.

In a weekly news conference on Monday, Iranian Foreign Ministry spokesperson Nasser Kanaani described Israel’s actions in Lebanon as “criminal,” and said that while the Islamic Republic is “not a warmonger… No measures and adventurism against Iran’s national security will go unanswered,” state-run IRNA reported.

How has the US reacted?

Attention has focused on how the once-mighty US is increasingly powerless to rein in its ally or to influence other major belligerents in a fast-worsening regional crisis.

US officials told CNN they were informed by their Israeli counterparts that the incursion into Lebanon was expected to be limited in scope and duration.

The White House on Monday said Israel has the right to defend itself, but warned of the risk of “mission creep” in a ground operation that could ultimately broaden in scope and turn into a longer-term incursion.

President Joe Biden last week unveiled a 21-day ceasefire proposal, backed by other US allies, that was almost immediately rejected by Netanyahu – to the frustration of the White House.

The US is a key provider of Israel’s weapons — it likely supplied the 2,000-pound bombs  used to kill Hezbollah’s leader — but Biden and his advisers have continued to call for a diplomatic resolution.

How has the world responded?

Several states and UN bodies have warned of the impact on civilians in Lebanon and the risk of further regional instability.

The European Union renewed its call for an immediate ceasefire between Hezbollah and Israel. In a statement on Monday, EU Foreign Policy Chief Josep Borrell called for “the respect of international humanitarian law in all circumstances,” and said the “sovereignty of both Israel and Lebanon has to be guaranteed.”

UNIFIL said in a statement that “any crossing into Lebanon is in violation of Lebanese sovereignty and territorial integrity,” urging “all actors to step back from such escalatory acts which will only lead to more violence and more bloodshed,” it added.”

French Foreign Minister Jean-Noel Barrot urged Israel on Monday “to refrain from any ground incursion” into Lebanon, and called on both sides to agree to a ceasefire.

The United Arab Emirates expressed “deep concern” over the recent escalations, fearing its “impact on regional stability,” the state-run Emirates News Agency (WAM) reported, adding that the Gulf state “reaffirmed its unwavering position towards the unity of Lebanon, national sovereignty, and territorial integrity.” The UAE also directed an urgent $100 million relief package to the people of Lebanon.

Jordan expressed “its rejection of the Israeli aggression” against Lebanon. Saudi Arabia said it “stresses the need to preserve Lebanon’s sovereignty and territorial integrity,” while Qatar expressed solidarity with Lebanon as well as “readiness to provide support to the people to confront the consequences of the Israeli aggression.”

Turkey condemned Israel’s ground operation, calling it “a violation of sovereignty and an unlawful act of occupation,” according to the state-run Anadolu news agency.

The United Nations’ agency for humanitarian emergencies (OCHA) warned of the devastating impact on civilians of the recent escalations in Lebanon. The UN agency urged the international community to “urgently promote de-escalation and ensure that all parties respect international humanitarian law, while prioritizing immediate humanitarian assistance to the affected people.”

The UN’s World Food Programme has also launched an emergency project to scale up food assistance for up to 1 million people in need in Lebanon.

CNN’s Tamara Qiblawi, Mostafa Salem, Ivana Kottasová, Jeremy Diamond, Lauren Izso, Tara John, Mick Krever, Eyad Kourdi, Joseph Ataman, Irene Nasser, Stephen Collinson, MJ Lee, Lex Harvey, Sarah El Sirgany, Abeer Salman and Mike Schwartz contributed reporting.