Ehud Barak, the Israeli defense minister, on right, with Prime Minister Benjamin Netanyahu.

As the Sabbath evening approached on Jan. 13, Ehud Barak paced the wide living-room floor of his home high above a street in north Tel Aviv, its walls lined with thousands of books on subjects ranging from philosophy and poetry to military strategy. Barak, the Israeli defense minister, is the most decorated soldier in the country’s history and one of its most experienced and controversial politicians. He has served as chief of the general staff for the Israel Defense Forces, interior minister, foreign minister and prime minister. He now faces, along with Prime Minister Benjamin Netanyahu and 12 other members of Israel’s inner security cabinet, the most important decision of his life — whether to launch a pre-emptive attack against Iran. We met in the late afternoon, and our conversation — the first of several over the next week — lasted for two and a half hours, long past nightfall. “This is not about some abstract concept,” Barak said as he gazed out at the lights of Tel Aviv, “but a genuine concern. The Iranians are, after all, a nation whose leaders have set themselves a strategic goal of wiping Israel off the map.”

The Nuclear Assassinations

When I mentioned to Barak the opinion voiced by the former Mossad chief Meir Dagan and the former chief of staff Gabi Ashkenazi — that the Iranian threat was not as imminent as he and Netanyahu have suggested and that a military strike would be catastrophic (and that they, Barak and Netanyahu, were cynically looking to score populist points at the expense of national security), Barak reacted with uncharacteristic anger. He and Netanyahu, he said, are responsible “in a very direct and concrete way for the existence of the State of Israel — indeed, for the future of the Jewish people.” As for the top-ranking military personnel with whom I’ve spoken who argued that an attack on Iran was either unnecessary or would be ineffective at this stage, Barak said: “It’s good to have diversity in thinking and for people to voice their opinions. But at the end of the day, when the military command looks up, it sees us — the minister of defense and the prime minister. When we look up, we see nothing but the sky above us.”

Netanyahu and Barak have both repeatedly stressed that a decision has not yet been made and that a deadline for making one has not been set. As we spoke, however, Barak laid out three categories of questions, which he characterized as “Israel’s ability to act,” “international legitimacy” and “necessity,” all of which require affirmative responses before a decision is made to attack:

1. Does Israel have the ability to cause severe damage to Iran’s nuclear sites and bring about a major delay in the Iranian nuclear project? And can the military and the Israeli people withstand the inevitable counterattack?

2. Does Israel have overt or tacit support, particularly from America, for carrying out an attack?

3. Have all other possibilities for the containment of Iran’s nuclear threat been exhausted, bringing Israel to the point of last resort? If so, is this the last opportunity for an attack?

For the first time since the Iranian nuclear threat emerged in the mid-1990s, at least some of Israel’s most powerful leaders believe that the response to all of these questions is yes.

At various points in our conversation, Barak underscored that if Israel or the rest of the world waits too long, the moment will arrive — sometime in the coming year, he says — beyond which it will no longer be possible to act. “It will not be possible to use any surgical means to bring about a significant delay,” he said. “Not for us, not for Europe and not for the United States. After that, the question will remain very important, but it will become purely theoretical and pass out of our hands — the statesmen and decision-makers — and into yours — the journalists and historians.”

By RONEN BERGMAN    NY TIMES