Israeli Defense Minister Ehud Barak and former Mossad chief Meir Dagan have a lot in common. They are both chubby and in their late sixties. They are both war heroes, decorated generals. And each rose to the highest positions in the Israeli defense establishment. But don’t mistake such biographical similarities for personal affinity. Barak and Dagan hate each other. Their animosity goes back years—and at the heart of their dispute is the critical question of how the Jewish state should deal with its enemies’ nuclear ambitions.In December 2010, together with some 30 Israeli defense and political journalists, I boarded a bus that took us to a building on the top of a hill overlooking Glilot junction, five miles north of Tel Aviv. We had come to Mossad headquarters for a meeting with Dagan, who was then the head of the agency. It was supposed to be an off-the-record briefing. But this being Israel, within hours after the meeting ended, most of what Dagan told us was on the Web and in the papers.What he said was shocking. The Mossad chief told us that Iran would obtain nuclear warheads by 2014 at the earliest, and thus, he argued, there was no need for an Israeli military strike for the time being. Dagan’s claim ran directly counter to the public line of Israel’s defense establishment: that Iran would obtain the bomb much sooner.Since that meeting more than a year ago, Dagan has been on a crusade to stop Israel from launching an imminent military strike against Iran. He has reiterated the argument that he laid out to us in Mossad headquarters—against a strike and in favor of sanctions and covert operations—at various public events and private conversations over the past year. And though Dagan is no longer head of Mossad, his view carries tremendous weight: His perspective on a possible Israeli strike is shared by many of Prime Minister Benjamin Netanyahu’s Cabinet ministers and Israel’s security establishment.Dagan’s campaign has enraged Barak and Netanyahu, who accuse him of undermining Israeli deterrence. Barak and Netanyahu support an Israeli military strike in the near future, and for the past few months, with increasing intensity, they have tried to create the impression that they are considering such an attack this year.Which view will prevail? At stake is the future of Israel, the lives of Iranians and Israelis, the supply of oil to the United States and the West, and the stability of the whole Middle East.***The roots of the tension within the highest level of Israel’s political-military leadership go back nearly five years, when Barak, Dagan, and the rest of the Cabinet were faced with the delicate question of whether to bomb Syria’s nuclear reactor in the Dir al-Zur region. In summer 2007, the Cabinet, led by then-Prime Minister Ehud Olmert, deliberated behind closed doors to discuss the assessments of Mossad and Israeli military intelligence of a big structure that Syria was secretly building near the Euphrates River. The undisputed conclusion was that Syria was constructing a reactor to produce plutonium for nuclear bombs and that the plans for the reactor had been provided by North Korea.The Cabinet’s overwhelming decision was to order the Israeli air force to launch a military strike before radioactive materials would be introduced and it would be too late. Barak was the most senior Cabinet member to oppose the idea, and he argued that Israel could wait a few more months. Olmert, then-Chief of Staff General Gabi Ashkenazi, Dagan, and other Cabinet ministers were astonished to hear it. They suspected that Barak had a hidden agenda motivated by his own ambition to be prime minister. That summer, Barak and the Cabinet knew that within three or four months the findings of an inquiry commission investigating the 2006 Lebanon war would be released. They expected the commission would blame Olmert for major failures of the war, and thus he would be forced to resign. Barak hoped to replace him.Over the course of a few weeks, Barak realized that he was in unsplendid isolation. Ultimately, he decided to join his Cabinet colleagues in approving the attack. (The Cabinet voted 13 to 1 to approve the attack. Avi Dichter, then minister of homeland security, opposed it.) In September 2007, eight U.S.-made Israeli F-16 fighter planes destroyed Syria’s nuclear ambitions when they bombed the reactor.Barak’s behavior during that process caused Dagan and other military leaders to lose their faith in him. As one senior official put it, “If he zigzagged then, what assures us that his motives this time are pure?” Indeed, three years ago in private conversation, Barak opposed a military strike by Israel against Iran. So, what made him change his mind? It’s not clear. One possibility is that he wants to please Netanyahu in the hopes that the prime minister will take him aboard Likud and reinstate him in the Defense Ministry after the next elections, which are set for November 2013 but most likely will be sooner.Continue reading: ‘When the sword is on our neck’\nDagan does not oppose a military strike as a matter of principle. But as a military man who witnessed the horrors of war, especially in the 1973 Yom Kippur War, for him an all out assault on Iran must be a last resort. “Only when there is an existential threat and the sword is on our neck” should we take military action, he told us in that meeting at Mossad headquarters.The former Mossad chief still believes that Israel has not yet arrived at that junction. According to Israeli intelligence, Iran has already crossed the “technological threshold,” which means that the Islamic Republic has mastered the craft of producing 20 percent enriched uranium. If it wishes, it is capable of enriching it to 90 percent, which is bomb-grade material. Despite the damage inflicted on its nuclear program by Mossad, CIA, and British MI6 in a series of covert operations, Iran still has at least 5,000 operational centrifuges—a sufficient number to spin uranium to bomb level (90 percent). It has also secretly conducted numerous laboratory tests and computer simulations in the process of weaponization, the final stage in assembling the bomb. All Iran needs now is the political decision to instruct its scientists to produce a bomb.What Dagan’s argument relies on is the belief that Iran has not yet made such a decision. In addition, once such a decision is made, Iran will need six to 18 months to produce its first crude atomic device. It will need another two years to make the bomb “deliverable,” i.e., miniaturize it to a size that can be fitted as a warhead on its Shihab 3 missile capable of reaching Israel or Saudi Arabia.All in all, according to Dagan, Israel and the West still have time to influence the Iranian regime by toughening sanctions in the mold of what the European Union decided to do two weeks ago (i.e., to stop purchasing oil from Iran by July). That decision was just supplemented on Monday by the White House’s directive to freeze the assets of Iran’s Central Bank. Then there are covert measures, like knocking off Iranian nuclear scientists and installing computer viruses like Stuxnet. If such measures fail to affect the Iranian regime, Israel or the United States will still have a window of opportunity to strike.This attitude is shared by the U.S. intelligence community and the Obama Administration, as Secretary of Defense Leon Panetta and Director of National Intelligence James Clapper have recently expressed. In an interview with 60 Minutes late last month, Panetta said: “The consensus is that, if they decided to do it, it would probably take them about a year to be able to produce a bomb and then possibly another one to two years in order to put it on a deliverable vehicle of some sort in order to deliver that weapon.”Barak and Netanyahu couldn’t see things more differently. In a recent article in the New York Times Magazine, Israeli journalist Ronen Bergman shared their thinking. He wrote that Barak—and I would add Netanyahu, too—is guided by three questions regarding Israel’s decision to strike. The first question is: Does Israel have the military capability to inflict severe damage on Iran’s nuclear facilities and significantly set back their progress? Question two: Will the international community sanction such an attack? And third: Is it necessary to do it now or in the near future? According to Bergman’s article, Barak is convinced that the answers to all these questions are yes, and thus Israel must attack Iran this year.However, in recent conversations with several senior Israeli air force commanders, intelligence chiefs, and Cabinet ministers, one can come to the opposite conclusion. Many of these leaders say that Israel lacks the military capability to paralyze or set back Iran’s nuclear program three to five years. Israel has a limited fleet of fighters and bombers, which can carry a limited weaponry load. It simply doesn’t have sufficient capabilities to carry out a prolonged campaign with a multitude of sorties. Such a sustained campaign can only be carried out by the United States.As to the second question—whether Israel has international backing—there is neither international support nor U.S. approval. And as Dagan, the majority of Israeli Cabinet ministers, the CIA, and others have made clear, there is no need to strike in the near future since there is still time before Iran produces its first bomb. Thus the answer to Barak’s three questions is no.Those who prefer to use a military option only when “the sword is on the neck,” as Dagan put it, point to the fact that the current combination of sanctions and covert operations is working. Indeed, there are many indications that the pressure on Iran is bearing fruit. The economy is deteriorating, inflation is up to 30 percent, and the Iranian currency was recently devalued by 10 percent. Earlier this week, Iran’s Supreme Leader Ayatollah Khamenei restated that the “cancerous tumor” of Israel should be wiped off the map. This should be understood as a sign that the regime is feeling the heat.The mullahs are in a sort of catch-22. They aspire to have nuclear weapons as deterrence against what they believe is an Israeli-Western threat to the regime. They want the bomb as an insurance policy to ensure their own survival. But in racing to get it, they may find themselves in a war that may actually bring down their regime.It is difficult to predict what Iran’s decision will be. Some experts tend to believe that as the international pressure increases, the Islamic Republic will slow down its program in order to stall for more time by pretending it wants to negotiate. But if they break out and rush to produce nuclear bombs, I believe that they most likely will be attacked. Not by Israel—but by the United States.Yossi Melman is a longtime reporter on strategic affairs, intelligence, and nuclear issues. He is writing a book about the history of the Israeli intelligence community.