When Iran agreed to a deal in 2015 that would require it to surrender 97% of the uranium it could use to make nuclear bombs, Russia and China worked alongside the United States and Europe to get the pact done.

The Russians even took Iran’s nuclear fuel, for a hefty fee, prompting celebratory declarations that Russian President Vladimir Putin could cooperate with the West on critical security issues and help constrain a disruptive regime in a volatile region.

Demonstrators show their support for Iran’s attack on Israel in Palestine Square in Tehran, Iran, Monday, April 15, 2024.

A lot has changed in the subsequent nine years. China and Russia are now more aligned with Iran’s “Axis of Resistance” to a U.S.-led order, along with the likes of North Korea. When President Joe Biden gathered the leaders of six nations for a video call from the White House on Sunday to plot a common strategy for de-escalating the crisis between Israel and Iran, there was no chance of getting anyone from China or Russia on the screen.

The disappearance of that unified front is one of the many factors that make this moment seem “particularly dangerous,” said Vali Nasr, an Iranian-born professor at Johns Hopkins University’s Paul H. Nitze School of Advanced International Studies, “maybe the most dangerous in decades.”

But it is hardly the only one.

Then-President Donald Trump’s decision to pull out of the Obama-era nuclear deal triggered a predictable counterreaction from Iran, and after a long pause, Iran resumed enriching uranium — some to near-bomb-grade quality. Today, it is far closer to being able to produce bomb-grade material, according to the International Atomic Energy Agency, than it was when the accord was in effect. Iran has consistently denied that it intends to build a weapon but has recently begun hinting at the need to bolster its “deterrent” against nuclear-armed adversaries.

Iran has surged ahead with its ballistic missile program, and several months before some of those weapons were unleashed on Israel this past weekend, all the remaining United Nations prohibitions expired. Iran has not only emerged as Russia’s most dependable foreign supplier of military drones, but it has also improved its own drone fleet by drawing lessons from their use in Russia’s assault on Ukraine.

Then-President Barack Obama’s pursuit of the 2015 nuclear deal was assailed by many Republicans as dangerously irresponsible at the time. Even some Democrats, though supportive of the details of the deal, worried that Obama was naive to hope it would bring about fundamental change in Iran.

With the latest escalation of tensions between Iran and Israel, Biden’s political opponents are now blaming the administration for having not taken a tougher line in recent years against Iran. They say that has left Israel in particular peril at a moment when it is mired in a war against an Iranian client group, Hamas, in the Gaza Strip.

“The White House signaled both obliviousness and weakness by not recognizing that today’s Middle East conflict is not Palestinians or Arabs against Israel, but an Iranian war against ‘the little Satan,’” John Bolton, who served as national security adviser to Trump and was a sharp opponent of the Iran deal, wrote Sunday.

“The sad truth is that Israeli and U.S. deterrence against Iran failed,” he said. He went on to urge — as he and a small group of Iran hawks have before — that Israelis seize the moment to “destroy Iran’s air defenses” and perhaps go after the Quds Force, Iran’s most elite units. In other words, take a course of escalation exactly the opposite of what Biden is urging.

Even among experts more supportive of Biden’s diplomacy in the region, many are concerned that now there are few levers to influence Iran, especially if Israeli Prime Minister Benjamin Netanyahu responds to the attack with a more calibrated retaliatory strike than the one Bolton is urging.

“We appear to be headed to an eventual Israel-Iran confrontation,” Nasr said.

“Iran and Israel are now the main protagonists in the Middle East,” he added. “They view each other as their most serious national security threats. There are no red lines or rules in place to contain their rivalry. The shadow war is now breaking into the open, and without some rules, they are on an escalatory path."

This was not the world Biden hoped for as he designed a strategy for his administration that focused on containing Russia’s disruptions in Ukraine and beyond, and competing vigorously with China. And in the first three years of Biden’s presidency, the Middle East seemed relatively calm, until the Oct. 7 terror attack by Hamas killed 1,200 Israelis, upended his priorities and plunged the White House back into a familiar cauldron.

Although Biden used intermediaries to help ensure that Iran’s retaliatory strikes over the weekend did not spin out of control — and Iran appeared intent on keeping indirect lines open — there is no direct communication between the U.S. and Iran, a major change from even a decade ago.

During the Iran negotiations, U.S. Secretary of State John Kerry spoke regularly, and directly, to his Iranian opposite number, Mohammad Javad Zarif, who had attended college and graduate school in the United States before the Iranian revolution.

As they haggled over the number of centrifuges Iran could build, they also defused potential crises. When a small U.S. naval vessel accidentally crossed into Iranian waters and its crew was seized, calls between the two men got them released in hours, averting another hostage crisis.

But that era is over. When the Biden administration came in, and sought in its first 18 months to revive some part of the 2015 deal, Ayatollah Ali Khamenei declared that there would be no direct talks with the administration. Notes and offers were passed through European interlocutors. The two sides seemed at the cusp of a deal in the summer of 2022; the Iranian negotiators took it back to Tehran, where new demands were added and the entire process fell apart.

Now, the fear of a general escalation has a new, lurking nuclear dimension.

The Iranians have not, from all available evidence, been racing for a bomb; their progress in uranium enrichment has been steady and deliberate. But as part of the pressure campaign on the West, they have largely blinded inspectors from the International Atomic Energy Agency, the world’s nuclear watchdog.

Inspectors have been barred from some sites. Some inspectors, from countries the Iranians have deemed unfriendly, have been denied entry. Surveillance cameras at some crucial sites have been removed. Questions about past activity at specific military locations have gone unanswered.

“The result is that I cannot offer assurances” that nuclear material has not been diverted to other facilities or weapons programs, Rafael Grossi, the Argentine diplomat who serves as director general of the United Nations agency, said in an interview before the outbreak of the missile barrage over the weekend.

Nuclear experts say one of their biggest concerns today is that Iran has every incentive to proceed with its nuclear program, both to taunt the West and to build what it always calls its “deterrent” against Israel, the undeclared nuclear weapons state in the region.

“That’s my concern — they have every motivation to accelerate,” James Clapper, director of national intelligence under Obama, said Sunday.

Other experts note that Israel’s success — with U.S. help — in shooting down almost all of the drones and ballistic missiles fired from Iran overnight Saturday could well lead Iranian military officials to conclude they need more powerful weapons, stationed closer to Israeli territory. And they may conclude that their logical next step is to move — overtly or covertly — toward a nuclear weapon.

For now, Biden is doing everything he can to persuade Netanyahu, with whom his relationship is fraught, to “take the win,” as he put it to him Saturday night, and not retaliate.

For their part, the Iranians have signaled that in their mind, the incident is over. They have avenged the deaths from an Israeli strike of seven commanders of Iran’s Revolutionary Guard. But “over” could simply refer to an end to the missile barrage, not other forms of escalation.

The best scenario would be that Iran recognizes the danger as well, as it did Saturday when it carefully telegraphed its intentions, which made it far easier for the Israelis, the U.S. and nearby Arab forces to intercept the incoming drones and missiles. That was a sign that Iran wanted to make a point but may not be ready to go to the brink of war.