The killing of Saleh al-Arouri, a top Hamas leader, on Tuesday deprives the group of one of its most skilled tacticians, who helped route money and weapons to its operatives in the Gaza Strip and elsewhere in the Middle East and integrated Hamas more tightly into Iran’s network of forces committed to fighting Israel, according to analysts.
But it was far from clear on Wednesday that his death would be a debilitating blow to the organization, which has rebuilt again and again after assassinations of its leaders, and remained agile enough to plot the Oct. 7 terrorist attacks in southern Israel.
Still, Mr. al-Arouri’s killing — in an explosion in a Beirut suburb that senior officials from Hamas, Lebanon and the United States ascribed to Israel — sets Hamas back at a highly vulnerable time, analysts say. Israel has not taken responsibility for his killing.
Israel’s overwhelming offensive in Gaza has significantly weakened the military strength of Hamas there, including its ability to manufacture rockets and other weapons. Mr. al-Arouri’s position, as Hamas’s de facto ambassador to Iran and Hezbollah, meant that he would have had an important role in the group’s efforts to rebuild militarily with help from foreign backers.
“Hamas will suffer, because it has lost one of its key strategists,” said Emile Hokayem, the director for regional security at the International Institute for Strategic Studies in London. “He was someone who did well managing high-level political relationships and also had credibility as a commander.”
Rebuilding its military capabilities “is going to be the problem for Hamas in the next phase, and it will likely be more dependent on foreign support as its base in Palestine weakens,” Mr. Hokayem added.
Mr. al-Arouri’s assassination also further internationalizes Israel’s war against Hamas, significantly raising the stakes for countries that host Hamas officials and putting new pressures on the group that could, if sustained, transform it.
In recent years, Hamas has operated as a network with nodes across the Middle East. Since 2007, it has been the de facto government for Gaza’s 2.2 million Palestinians, overseeing services like water and electricity while its armed wing frequently battled with Israel. Its operatives also organized covertly in the Israeli-occupied West Bank, while officials in other countries raised money to fund its operations, maintained relationships with its allies and communicated its views to journalists and foreign diplomats.
Mr. al-Arouri’s killing suggests that Hamas members can no longer operate risk-free in Lebanon, where Hamas officials have held frequent news conferences throughout the Gaza war. They may also need to be wary in Qatar, where the group’s senior political leaders have an office, and in Turkey, where senior Hamas figures regularly spend time.
“The movement is going to change significantly,” Mr. Hokayem said.
Israel, the United States and other countries consider Hamas a terrorist organization, limiting where its leaders can go. Even countries that have not outlawed the group could hesitate to welcome its operatives, fearing assassinations on their soil.
Mr. al-Arouri met with Iran’s supreme leader, Ayatollah Ali Khamenei; grew close to Hassan Nasrallah, Hezbollah’s powerful leader; and helped build up Hamas’s forces in Lebanon, along Israel’s northern border.
Even before the war, Mr. Nasrallah had warned that any assassinations in Lebanon would meet with a strong response. He is expected to speak publicly on Wednesday, in an address that was scheduled before Mr. al-Arouri’s killing.
Imad Alsoos, a research fellow from Gaza at the MECAM center at the University of Tunis, said the loss of Mr. al-Arouri would not cripple Hamas. Israel, he said, had assassinated many Hamas leaders over the decades without permanently undermining the group’s ability to rebuild — or to plot the Oct. 7 attack.
Those killings made the group agile, he said, and its leaders rose to prominence through elections and their legitimacy inside the organization, not because of personal charisma or religious credentials, traits that could make individual leaders harder to replace.
“Inside Hamas, you have always a certain hierarchy, and replacement is very smooth,” he said. “Within Hamas, the personality is not the source of power.”
Over several years, operating mostly from the shadows, Mr. al-Arouri worked to upgrade the organization’s fighting abilities and reorient its position in the wider Middle East.
His deadly effectiveness led the United States to offer up to $5 million for information on his whereabouts and moved him up the ranks of Israel’s kill list.
Israel had vowed after the deadly Oct. 7 assault to hunt down Hamas leaders wherever they are. Mr. al-Arouri was the highest-ranking Hamas official to be killed since the war in Gaza began nearly three months ago.
“The loss of someone so intimately involved in both tactical operations and strategic diplomacy is a serious setback for Hamas,” Hanin Ghaddar and Matthew Levitt wrote in an analysis for the Washington Institute for Near East Policy. They said that Mr. al-Arouri had “played a critical role as one of the group’s primary and most effective liaisons to both Hezbollah and Iran.”
The Hamas-led assault on Israel killed about 1,200 people, and 240 others were taken back to Gaza as captives. In the months since, Israel has retaliated with overwhelming force that it says is intended to destroy Hamas, reducing swaths of the territory to rubble, displacing 85 percent of its population and killing more than 20,000 people, about 70 percent of them women and children, according to health officials in Gaza, who do not differentiate between civilians and militants.
The war has also had ripple effects across the region.
This week, Turkish news outlets heavily publicized the arrests of 33 people suspected of spying for Israel, claiming they had been involved in “reconnaissance” and “pursuing, assaulting and kidnapping” foreigners in Turkey.
Turkey’s president, Recep Tayyip Erdogan, who has voiced support for Hamas and criticized Israel, previously warned that Israel would suffer “serious consequences” if it attacked Hamas members in Turkey.
Officials in Qatar have not announced any changes in the status of the Hamas office in their country.
Mr. al-Arouri’s reorientation of Hamas toward Iran and its regional allies will likely shape the group’s future, and could determine where its leaders set up shop.
Hamas had received support from Iran since soon after the group’s foundation in 1987, but the relationship grew strained after Hamas closed its office in Syria, a close Iranian ally, in 2012 amid Syria’s brutal suppression of an antigovernment uprising.
Mr. al-Arouri was among a group of Hamas leaders who considered that decision a mistake, and he worked closely with Yahya Sinwar, a leader in Gaza, to rebuild ties with Iran and its regional allies, according to regional officials and analysts who track the group.
“The position of al-Arouri and Sinwar was that the Arab camp was precarious and we can’t stand on it,” said Mr. Alsoos at the University of Tunis. “They decided that they had to ally with Hezbollah and Iran so that they could support them militarily and financially.”
That approach received a boost in 2017, when both men were promoted in internal Hamas elections. Mr. Sinwar, who was close to Hamas’s military wing, became the group’s leader in Gaza, and Mr. al-Arouri rose to Hamas’s second-highest post and took charge of its West Bank operations.
Mr. al-Arouri’s role in building up Hamas’s forces in Lebanon pointed to a close relationship with Mr. Nasrallah, the Hezbollah leader, said Mr. Alsoos.
“They don’t work independently. They work with Hezbollah,” he said of Hamas fighters in Lebanon. “That means that Nasrallah trusted al-Arouri enough to allow him to do that.”
Eric Schmitt contributed reporting from Washington.