Two weeks ago, Prime Minister Rishi Sunak of Britain was facing a chorus of calls to cut off arms shipments to Israel because of its devastating war in Gaza. On Monday, Mr. Sunak saluted the British warplanes that had shot down several Iranian drones as part of a successful campaign to thwart Iran’s attack on Israel.
It was a telling example of how the clash between Israel and Iran has scrambled the equation in the Middle East. Faced with a barrage of Iranian missiles, Britain, the United States, France and others rushed to Israel’s aid. They set aside their anger over Gaza to defend it from a country they view as an archnemesis, even as they pleaded for restraint in Israel’s response to the Iranian assault.
Prime Minister Benjamin Netanyahu, whose approval of a deadly airstrike on a meeting of Iranian generals in Damascus on April 1 provoked Iran’s retaliation, has managed to change the narrative, according to British and American diplomats and analysts. But it could prove to be a fleeting change, they said, if Mr. Netanyahu orders a counterstrike damaging enough to pitch the region into wider war.
“We would urge them to take the win at this point,” Mr. Sunak said in Parliament, borrowing a phrase that President Biden used in a phone call with Mr. Netanyahu on Sunday after Iran’s attack had been mostly repelled.
Mr. Sunak was expected to have his own call with Mr. Netanyahu on Tuesday, part of a full-court press by European leaders to urge him not to allow the clash with Iran to spiral uncontrollably. President Emmanuel Macron of France, which played a supporting role in the military operation, told a French news channel, “We will do everything to avoid a conflagration — that is to say, an escalation.”
The German foreign minister, Annalena Baerbock, signaled the limits of support for an Israeli counterattack. “The right to self-defense means fending off an attack,” she said. “Retaliation is not a category in international law.”
Analysts said the Western pressure on Mr. Netanyahu over Iran would be even more intense than over Gaza because a full-blown war between Israel and Iran would be far more destabilizing — geopolitically and economically — than the Israeli campaign to root out Hamas militants in Gaza. It would force a series of hard decisions on Israel’s allies in quick succession, requiring them to rethink their entire strategies for the region.
While the ferocity of Israel’s assault in Gaza has galvanized much of world opinion against it, particularly after the Israeli strike that killed seven staff members of World Central Kitchen, it has not convulsed financial markets or turbocharged oil prices, as a war between Iran and Israel almost certainly would.
Such a war would likely draw in the United States and possibly Britain, which played its traditional role of wingman in the American-led effort to shoot down Iranian drones and missiles. That could have volatile political effects in both countries, where voters are going to the polls later this year.
“If every time Israel decides to punish Iran, it creates a massive tumult in Washington and London, these countries are going to pressure Israel,” said Vali R. Nasr, a professor at the Johns Hopkins School of Advanced International Studies who served in the Obama administration. “There’s going to be a major international effort to build cordons around Israel’s behavior toward Iran.”
Daniel Levy, a former Israeli peace negotiator who now runs the U.S./Middle East Project, a think tank based in London and New York, said the difference in global stakes between the Iran and Gaza conflicts was evident in how Western governments dealt with Israel on each issue.
“There’s been this united public response defending Israel on Iran, with strong private messaging to Israel, ‘Don’t you dare,’” Mr. Levy said. “While on Gaza, there’s a lot of public hand-wringing but a lack of will to be tough in private.”
“Gaza doesn’t directly pull the United States into a war,” he said. “So, they still believe they can tiptoe through the raindrops.”
On Monday, Mr. Sunak insisted that the latest crisis would not take Israel off the hook for the civilian death toll in Gaza. The prime minister repeated his call for a humanitarian pause that would lead to a sustainable cease-fire.
“Nothing that has happened over the last 48 hours affects our position on Gaza,” Mr. Sunak said. “The whole country wants to see an end to the bloodshed and to see more humanitarian support going in.”
But even before the Iranian assault on Israel, the British government was resisting calls for a halt to arms shipments. Officials declined to disclose confidential legal advice on whether Britain’s arms trade with Israel violated international law, as several prominent lawyers have argued.
In Washington, Speaker Mike Johnson said on Monday that he planned this week to advance a long-stalled national security spending package to aid Israel, Ukraine and other American allies.
Cutting off British weapons is now on the “back burner” because of Iran, said Peter Ricketts, a former British diplomat and national security adviser whose call for a suspension in sales earlier this month helped kick off the debate. It could be moot altogether, he said, if Israel declared a cease-fire and struck a deal to release hostages held by Hamas — something it has yet to do.
“Netanyahu must have calculated when he hit the Iranian Consulate in Damascus that the Iranians would retaliate, and that this would swing the Americans and their Western allies behind Israel,” Mr. Ricketts said. “And that’s worked, remarkably well.”
“It’s all gain for Netanyahu,” Mr. Ricketts said, “if he has the wisdom to take the win, or at least to retaliate in a limited way.”
Martin S. Indyk, a former American ambassador to Israel, said a limited Israeli response was the most likely scenario. “Netanyahu will respond — he has to — but not in a way that requires the Iranians to retaliate, and pocket the good will from Biden for the war in Gaza,” he said.
“The war is now out in the open,” Mr. Indyk said of Iran and Israel. “I suspect it will make both sides more cautious and more wary of the intentions of the other — more on a knife’s edge than before.”
The challenge for Europe and the United States, some analysts said, is that of all the countries in the region, Israel has the greatest incentive to escalate hostilities with Iran. It has struggled to eradicate Hamas in Gaza and has become more diplomatically isolated because of the war’s humanitarian toll.
Even Mr. Netanyahu and Mr. Biden have been at odds, calling into question the support of Israel’s biggest backer. But Mr. Biden, analysts said, cannot afford a wholesale rupture with Israel, especially if it finds itself in an existential conflict with Iran and if that conflict unfolds during an election year.
“The Israelis have been trying to put the Americans in a position where they have no choice,” said Jeremy Shapiro, research director of the European Council on Foreign Relations. “For all the protests of the Biden administration, they’re in a difficult place. What are they going to do if the Israelis do escalate?”
