Yossi Melman writes: 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.

In Melman’s analysis of the struggle between Dagan and Barak, he pays a lot of attention to Israel’s attack on a nuclear reactor that Syria was alleged to be constructing in 2007. At the time and no doubt still now, there are those who viewed these allegations as part of a neocon conspiracy. The Syrians themselves claimed that the facility which got flattened in the Israeli attack was an agricultural research facility. Were that the case, it’s hard to understand why Bashir Assad would have failed to then make use of such a valuable propaganda opportunity. Western reporters could have been escorted around the site and shown all the shattered plant pots. Instead, bulldozers were swiftly moved in to bury every last trace of whatever the Syrians had been constructing. If they wanted to prove they had been falsely accused, this was a strange way of going about it.