Just 24 hours before he took to the podium on Wednesday, Hassan Nasrallah, the head of Lebanon’s powerful armed group Hezbollah, was preparing to deliver a speech commemorating another of Israel’s former arch-foes, Qassem Soleimani, the Iranian commander killed in a US drone strike four years ago to the day.

But in the wake of the suspected Israeli assassination on Tuesday of Saleh Arouri, a top Hamas leader killed in the heart of Hezbollah’s stronghold in southern Beirut, Nasrallah revised his comments to commemorate not just one of his closest allies, but two.

In a highly anticipated speech on Wednesday that gained new significance in the wake of Arouri’s assassination, Hezbollah’s leader denounced the attack in Lebanon’s capital as a “dangerous” milestone, pledging revenge for the killing and threatening to meet any wider Israeli conflict with unrestrained warfare.

“If the enemy considers waging a war against Lebanon, our battle will be without boundaries or rules,” Nasrallah said. “We are not afraid of war. Those who think of going to war with us will regret it. War with us will come at a very, very, very high cost.”

“Yesterday’s crime will not go unpunished,” he warned ominously in his closing.

But Nasrallah refrained from saying exactly how his group would respond to the assassination, adding that he would instead discuss the killing of Arouri in more depth in another speech on Friday. Despite a string of cross-border attacks on Israel by Hezbollah in the wake of Arouri’s assassination, none so far have signalled a marked escalation.

Israel has not publicly accepted or denied responsibility for the killing, but American and Lebanese officials have said Israel carried it out.

Hezbollah’s seeming hesitancy to react too soon to the killing fit with analysts’ assessment that the assassination on Lebanese soil had significantly complicated Hezbollah’s calculations regarding its escalating battle with Israel.

“It is a very uncomfortable moment for Hezbollah,” said Emile Hokayem, the director for regional security at the International Institute for Strategic Studies. “It is not something that can be brushed under the carpet very easily.”

Nasrallah had long warned that any assassinations on Lebanese territory would necessitate a strong response. But now, with the war in the Gaza Strip bringing regional tensions to a boiling point, any significant escalation would likely spell catastrophe. “He really has his back against the wall,” Hoyakem said.

Nasrallah dedicated much of his speech Wednesday to reaffirming Hezbollah’s steadfastness in the war that began with the Hamas-led attack launched from Gaza against Israel on October 7.