"If Iran goes nuclear it will have negative dimensions for the world, for the region, for the freedom of action Iran will permit itself," Chief of Staff Lt. Gen. Benny Gantz told Haaretz in an Independence Day interview.

That freedom of action might be expressed "against us, via the force Iran will project toward its clients: Hezbollah in Lebanon, Islamic Jihad in Gaza. And there's also the potential for an existential threat. If they have a bomb, we are the only country in the world that someone calls for its destruction and also builds devices with which to bomb us. But despair not. We are a temperate state. The State of Israel is the strongest in the region and will remain so. Decisions can and must be made carefully, out of historic responsibility but without hysteria," Gantz said.

Both 2012 and 2013 are seen as critical with regard to Iran's nuclear program. At his rare public appearances Gantz has taken a cautious approach to the issue - mentioning the military option, whose development and preparation he oversees, while leaving the door open to international negotiations with Iran. His language is far from the dramatic rhetoric of Prime Minister Benjamin Netanyahu, and is usually free of the Holocaust comparisons of which Israeli politicians are so fond.

Asked whether 2012 is also decisive for Iran, Gantz shies from the term. "Clearly, the more the Iranians progress the worse the situation is. This is a critical year, but not necessarily 'go, no-go.' The problem doesn't necessarily stop on December 31, 2012. We're in a period when something must happen: Either Iran takes its nuclear program to a civilian footing only or the world, perhaps we too, will have to do something. We're closer to the end of the discussions than the middle."

Gantz says the international pressure on Iran, in the form of diplomatic and economic sanctions, is beginning to bear fruit. "I also expect that someone is building operational tools of some sort, just in case. The military option is the last chronologically but the first in terms of its credibility. If it's not credible it has no meaning. We are preparing for it in a credible manner. That's my job, as a military man."

Iran, Gantz says, "is going step by step to the place where it will be able to decide whether to manufacture a nuclear bomb. It hasn't yet decided whether to go the extra mile."

As long as its facilities are not bomb-proof, "the program is too vulnerable, in Iran's view. If the supreme religious leader Ayatollah Ali Khamenei wants, he will advance it to the acquisition of a nuclear bomb, but the decision must first be taken. It will happen if Khamenei judges that he is invulnerable to a response. I believe he would be making an enormous mistake, and I don't think he will want to go the extra mile. I think the Iranian leadership is composed of very rational people. But I agree that such a capability, in the hands of Islamic fundamentalists who at particular moments could make different calculations, is dangerous."

About three months ago Gantz's U.S. counterpart, Chairman of the Joint Chiefs of Staff Gen. Martin E. Dempsey, visited Israel as his guest. "We speak a great deal with the Americans. It's not on the level of a discussion, where I want something concrete and he forbids it. We are partners. We and the United States have a large common alignment of interests and relations, but America looks at America and Israel [looks at] Israel. We aren't two oceans away from the problem - we live here with our civilians, our women and our children, so we interpret the extent of the urgency differently. America says its piece openly, and what it says in the media is also said behind closed doors. It cannot be translated into lights, red or green, because no one is asking them anything in that regard."

Critical decisions

Gantz knows that in the event of another war he will face time pressures as a result of enemy operations against the home front. The IDF will have to bring massive force to bear from the outset, employing most of the means at its disposal quickly and without hesitation or delay.

Ground operations, long-distance fire and in-depth operations as well?

"I don't pretend to determine that now. I am preparing for full deployment of our capabilities. The political leadership will have to take courageous, painful decisions. There are a certain number of critical decisions in a war. The chief of staff makes about 10 of these in his sphere of responsibility in wartime, and the political leadership makes about half this number."

These decisions, Gantz knows, will be made under a barrage of rockets and missiles against civilian areas.

In light of the Arab Spring, Israel's military preparedness must now include a much greater and more varied range of arenas and possibilities.

"I don't know what will happen in Syria, but presumably the Golan Heights won't be as quiet as before. I cannot remove Syria from the military equation, nor Lebanon. I assume that if there are terror threats from the Golan or Lebanon I'll have to take action. I cannot do everything by 'stand-off' [remote]. The enemy's fire capabilities have developed at every distance, four or five times what they were in the Second Lebanon War and four or five times compared to the Gaza Strip before Operation Cast Lead, not to mention the new ground-to-air missile in Syria. I go to sleep with the understanding that what we did in the recent long and comprehensive exercises could happen in reality."

The IDF is also being used as a battlefield for the cultural and political wars of outside forces. The latest skirmish followed Gantz's dismissal of Lt. Col. Shaul Eisner, deputy commander of the IDF's Jordan Valley brigade, for hitting a left-wing activist from Denmark in the face with a rifle. Gantz terms the political interference in the affair a disaster.

"I don't see anyone benefiting from this story. I made my decision, and it's behind me. I don't understand what the right is defending, what the left is attacking. Who turned it into a political matter? Do you have to be a religious right-winger with a kippah in order to be resolute? Do you have to be a leftist in order to be principled? Where did that idiocy come from? Eisner made a professional error and a specific ethical mistake."

The interview with Gantz took place right after additional videos of the incident were made public, showing Eisner hitting additional left-wing activists.

"I didn't like even the first blow I saw. I will not cover for people so that others will say I backed them up. The lieutenant colonel erred and failed, and it's done and dusted. We are an army that uses force, not violence."

Measured, thoughtful and practical

With regard to another delicate issue, Gantz says he believes the IDF could draft more ultra-Orthodox men if an alternative to the Tal Law, recently overturned by the High Court of Justice, can be found.

"It's for the politicians to decide. What I'm looking for is equality in service," he says.

The end of his predecessor's assignment was tarnished by the so-called Harpaz affair, in which Lt. Col. Boaz Harpaz allegedly forged a document in a bid to keep Yoav Galant from being appointed chief of staff. Gantz received the draft report of the State Comptroller's Office on the affair last month. When the final version is issued Gantz will face career decisions about several figures connected to the affair, including Col. Erez Weiner, aide to former Chief of Staff Gabi Ashkenazi.

Gantz believes it is important that the final version be issued before State Comptroller Micha Lindenstrauss ends his term, at the beginning of July.

"At every opportunity I say to the comptroller, please, go to it."

As in our previous conversations, now too Gantz comes across as a measured, thoughtful and practical person. Only a few dozen steps separate him from his previous office, that of the deputy chief of staff, but the distance between them is unfathomable.

"I enjoy being here but also feel the gravity of the responsibility. I always said my favorite position was company commander in the Paratroop Brigade. As a company commander you have absolute definitions: the mission, the people. The rest we can manage. Here, I can't pass on the responsibility to anyone else. The buck really does stop here. That's why I say that occasionally I doze off but I never really sleep."