US and Israeli intelligence agencies are working to determine whether an expected Israeli ground offensive against Hamas in the Gaza Strip could prompt Hezbollah to launch a large-scale military campaign against Israel from Lebanon, US and Israeli officials said.
U.S. officials said they believed the deployment of two carrier strike groups, each consisting of an aircraft carrier, its aircraft and several accompanying warships, had — for now — deterred Hezbollah from attacking Israel in a major way. Israel has also reinforced its northern border following an attack on Hamas on October 7, which killed 1,400 people.
Israeli and American officials currently assess that Hezbollah leader Hassan Nasrallah does not want an all-out war with Israel, fearing the damage it would do to his group and Lebanon. US officials said that assessment could change as more intelligence is gathered and events unfold.
In addition, Israeli Prime Minister Benjamin Netanyahu vetoed his government’s proposals for a preemptive strike against Hezbollah, according to U.S. officials and others briefed on the discussions.
Keeping the war confined to Gaza is a key American and Israeli priority. A significant campaign by Hezbollah, the Iranian-backed Lebanese Shiite group, would force Israel to fight on two fronts simultaneously, a tall order. It could also draw the United States into the conflict, potentially by launching airstrikes against Hezbollah targets.
Immediately after the Hamas attack, American and Israeli intelligence agencies concluded that Mr. Nasrallah was surprised by the scale and intensity of the attack. It was part of a growing body of evidence that neither Hezbollah nor Iran helped plan such a major Hamas attack, said US and allied officials, who spoke on condition of anonymity to reveal sensitive details of the crisis.
Spy agencies have long assessed that Mr. Nasrallah, whose group waged a 33-day war with Israel in 2006, did not want an all-out conflict with Israel, despite Hezbollah’s persistent anti-Israel rhetoric.
Some Iranians disputed those estimates, claiming that Mr. Nasrallah helped plan Hamas attacks. And Western intelligence is imperfect. American and Israeli officials, for example, did not believe that Hamas wanted to launch such a large-scale operation against Israel before the October 7 attack.
American officials are increasingly concerned that Mr. Nasrallah is under pressure from hardliners in the group to engage in the kind of full-scale war he has publicly called for but, US and Israeli officials say, has privately sought to avoid.
What the intelligence agencies are trying to determine is whether it is now more likely that Mr. Nasrallah to take actions he has previously avoided, what those actions would be, and whether the threat of direct American involvement on Israel’s side would be enough to keep him at bay, and if so, for how long.
Before the October 7 attack, according to Israeli officials, Mr. Nasrallah saw Israel as a particularly weak point in its history. But Israel’s response to the attack, including intense airstrikes on Gaza that killed 2,808 people, and preparations for a ground offensive, may have changed Hezbollah’s strategy, a senior Israeli defense official said.
This is one of the reasons why current US intelligence agencies believe that Mr. Nasrallah wants to keep his organization out of a major war, US officials said.
Israel’s northern border remains tense.
Clashes along the border with Lebanon — the most serious since the 2006 war — and Israeli airstrikes inside Syria have fueled fears of a wider conflict in the region.
Israel evacuated the northern border and reinforced it with military units to deter any potential attack, but clashes broke out on Sunday and Monday. Hezbollah fired on an Israeli tank and other positions on Monday, while Israel responded with artillery fire.
Although serious, Hezbollah’s attacks are generally quite contained. .
Hezbollah appears to have calculated that the types of attacks it has carried out so far are enough to show solidarity with Hamas, but not enough to provoke a large-scale response from Israel, according to an Israeli defense official.
But Israeli officials warned that the northern front remained a vital concern. Mr. Nasrallah may be under pressure to step up attacks. If a stray attack kills a large number of people, Israel could respond with far greater force, according to Israeli officials.
Hezbollah poses a much more serious threat than Hamas because of its vast arsenal of precision-guided missiles and thousands of experienced fighters.
“There is a risk of this conflict escalating, opening up another front in the north and, of course, Iranian involvement,” Jake Sullivan, President Biden’s national security adviser, told CBS News on Sunday.
“He wants to send a very clear message of deterrence to any country or any actor that would try to take advantage of this situation,” Mr. Sullivan added, referring to Mr. Biden.
In 2006, Hezbollah fighters ambushed an Israeli border patrol, killing three soldiers and capturing two others, leading to weeks of fighting that killed more than 1,000 Lebanese, mostly civilians, and an estimated 165 Israelis, mostly soldiers.
Both sides saw the war as having different outcomes, cementing Hezbollah in Lebanon as a powerful military and political force, but also causing massive damage in Lebanon.
Since then, Hezbollah has expanded its arsenal of rockets and missiles, many of which are provided by Iran or acquired with Tehran’s support. Although the border remains volatile, Israel and Hezbollah have largely managed to keep tensions low to prevent another major escalation.
For the past eight years, for example, the Israeli military has tried to avoid killing Hezbollah fighters, even when targeting other targets in Syria and Lebanon.
Israeli officials believe their strategy for managing the conflict with Hezbollah has been largely successful.
American and Israeli intelligence agencies supported that assessment with their analysis that Mr. Nasrallah has been wary of provoking another all-out war, which he believes could cause significant damage to his organization and weaken his power. In order to reduce the chances of this happening, Mr. Nasrallah has kept cross-border attacks rare and relatively small, Israeli officials said.
In turn, Israeli officials said they believed Israel’s muted responses to Hezbollah provocations reduced pressure on Mr. Nasrallah to further escalate the conflict, shortening any cycle of violence and allowing peace to be restored.
American officials said Mr. Nasrallah’s next moves were likely to depend on how Israel’s ground war in Gaza played out. American and Israeli officials fear that Mr. Nasrallah may no longer be able to resist pressure to open the northern front as Palestinian casualties mount during the ground invasion.
“If Hamas looks like it’s going to be destroyed, Hezbollah will be under incredible pressure to get directly involved and open up the northern front,” said Mick Mulroy, a former senior Pentagon official and CIA officer. “The more civilians are killed, the more anger will come from people in the region. This will put more pressure on Hezbollah to join the fight or lose credibility.”