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The past 48 hours in the Middle East – in which Israel killed Hezbollah leader Hassan Nasrallah and continued to bomb the Iran-backed group across Lebanon – have renewed fears that this long-running conflict could escalate into a larger regional war.

The killing of Nasrallah in a series of massive Israeli airstrikes on his underground headquarters in Beirut on Friday represents a significant escalation in the conflict between Israel and the Lebanon-based militant group, which has been firing on Israel since the start of the war against Hamas in the Gaza Strip.

It is also the latest in a series of major blows for Hezbollah, which has now lost several commanders and was already reeling after its members’ pagers and walkie-talkies exploded earlier this month, killing dozens of people and maiming thousands.

Israel has warned that a “new era” of war would begin if its “center of gravity” shifts north, referring to the Lebanese border. One of its stated war goals is the return of tens of thousands of its own civilians who were displaced by cross-border fighting.

Lebanese government officials say hundreds of thousands have been displaced inside Lebanon due to recent fighting, while more than a thousand have been killed since airstrikes escalated last week.

Israel has raised the possibility of a ground attack into Lebanon, which if carried out would be the fourth Israeli invasion of the country in the last 50 years.

Hezbollah has vowed it will “continue its struggle to confront the enemy,” while Iran, which supports the group as part of its network of regional proxies, has pledged its solidarity.

Here’s what we know so far and where it might go next.

Israel reportedly struck Hezbollah targets in the Lebanese capital Beirut and elsewhere in the country on Friday and Saturday, including the attack on the capital’s southern suburbs that killed Nasrallah.

Some of the strikes occurred in densely populated areas, with residential buildings being leveled. Israel has said Hezbollah stores weapons in civilian buildings, which the group denies, and accuses Hezbollah of using residents as “human shields.”

Lebanese civilians say they cannot heed Israeli military warnings to avoid places where Hezbollah operates because the group is extremely secretive. The warnings often come just a few minutes before a building is hit.

Residents of Beirut’s southern suburbs are fleeing Israeli bombardment. Many sleep in public places and no longer have space in makeshift accommodation.

The latest attacks came after Israeli Prime Minister Benjamin Netanyahu rejected a ceasefire proposal negotiated by the United States and France that called for a 21-day pause in fighting on the Israel-Lebanon border.

The White House said it had “no knowledge of or involvement in Israel’s Friday attack on Beirut.” US President Joe Biden described Nasrallah’s death as a “measure of justice for his many victims”, including Americans, and called for de-escalation in conflicts in the Middle East.

The US sees the possibility of a limited ground attack in Lebanon as Israel moves troops to its northern border, CNN previously reported, citing a senior administration official and a US official. However, the officials stressed that Israel appears to have not yet made a decision on whether to carry out a ground attack.

Israel Defense Forces spokesman Peter Lerner said earlier Saturday that the military was preparing for the possibility of a ground attack, but that it was only one option being considered.

In the wake of Nasrallah’s assassination – and the attack on pagers and walkie-talkies – Hezbollah’s remaining leaders will likely ponder how to meet, communicate and respond.

Some of the factors that will influence this response – such as the extent to which Israeli strikes have depleted the group’s ammunition – remain unknown. However, analysts say the setbacks the group has faced are unlikely to completely weaken it.

“Hezbollah has suffered the biggest blow to its military infrastructure since its founding,” said Hanin Ghaddar, senior fellow at the Washington Institute and author of “Hezbollahland.”

However, the group still has qualified commanders as well as many of its most powerful forces – including precision-guided missiles and long-range missiles that could cause significant damage to Israel’s military and civilian infrastructure, Ghaddar said.

To date, there has been no major rocket fire from Hezbollah that has caused significant damage to Israeli targets. And even after Nasrallah’s assassination, the group has yet to launch a major retaliatory strike on a scale that could overwhelm Israel’s Iron Dome air defense system and compromise its power grid.

But recent developments open up the potential for change.

According to Jonathan Panikoff, a former senior intelligence official specializing in the region, Hezbollah will almost certainly respond.

Another important question is to what extent Iran might interfere.

The state appeared wary of falling into direct conflict with Israel, even as its long-running shadow war has become even more public in recent months – and observers say direct Iranian retaliation is also pushing the US further into the conflict could pull in.

A senior U.S. official said the U.S. believes Iran will intervene in the conflict if it believes it is about to “lose” Hezbollah. According to this official and another person familiar with the intelligence, the combined impact of Israel’s operations against Hezbollah had already driven hundreds of fighters from the battlefield.

The Iranian embassy in Lebanon called Nasrallah’s killing a “serious escalation that changes the rules of the game” in a social media post on Friday and said the perpetrator would be “appropriately punished and disciplined.”

Iran’s envoy to the United Nations also called for an emergency Security Council meeting on Saturday to “strongly condemn Israel’s actions.”

But the space for diplomacy appears to be limited, especially since months of work on a ceasefire agreement for the war in Gaza have produced little lasting progress.

Aaron David Miller, former US State Department Middle East negotiator, pointed to the ongoing conflicts between Israel and Hamas, between Israel and Hezbollah and between Israel and Iran, to CNN: “None of these wars of attrition are going to end anytime soon…it.” There are no transformative, diplomatic Hollywood endings.”

“At best it is a question of deterrence, management and perhaps, if Hezbollah, the Israelis and the Iranians are open to it… agreements that contain the conflict,” he said.

CNN’s Abbas Al Lawati, Mostafa Salem, Irene Nasser, Alex Stambaugh and Dana Karni contributed to this report.