Al-Arouri’s killing is a blow to Hamas, though likely not a debilitating one, analysts say.

The killing of Saleh al-Arouri deprives Hamas of one of its most skilled tacticians, who helped route money and weapons to its operatives in Gaza and elsewhere in the Middle East and integrated the group more tightly into Iran’s network of forces committed to fighting Israel, according to analysts.

But it was far from clear 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 despite years of Israeli military and intelligence efforts to weaken it.

Still, Mr. al-Arouri’s killing — in a strike in a Beirut suburb on Tuesday that senior officials from Hamas, Lebanon and the United States ascribed to Israel — sets Hamas back at the most vulnerable time in its history, analysts said.

Israel’s overwhelming offensive in Gaza has significantly weakened the group’s military strength 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. Israel has not taken responsibility for his killing.

“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. “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 internationalized 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 suggested 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, and even countries that have not outlawed the group could hesitate to host 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 on Lebanese territory would meet a strong response. He is expected to speak publicly again 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 dozens of Hamas leaders over the decades without permanently undermining the group’s ability to rebuild — or to plot the Oct. 7 attack.

Those killings had 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.

“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.”