Israeli Prime Minister Ariel Sharon's departure from the right-wing Likud Party forced the scheduling Wednesday of new elections in March. Following a background report, two experts discuss the factors driving Sharon's actions and what might come next.

MARGARET WARNER: Once again, as he has so often in the past quarter century, Ariel Sharon has caused an earthquake in Israeli politics.

On Monday, Sharon bolted from the right-wing Likud Party he co-founded, and announced he would form a new one. That forced today's announcement of new elections in March.

ARIEL SHARON (Translated): After much soul searching, I decided today to quit the Likud. The Likud in its present configuration cannot lead the nation to its national goals. I founded the Likud over 30 years ago to serve the nation and give hope to the people of Israel. Unfortunately, it is no longer there.

MARGARET WARNER: Sharon's move culminated months of tension within his party, particularly over his decision to withdraw from Gaza and four West Bank settlements.

The 77-year-old Sharon first made his mark as a warrior. He fought in the 1948 Arab-Israeli War after the creation of the Jewish state, and as a soldier he developed a reputation for daring but sometimes reckless maneuvers.

In the 1956 Sinai War, Sharon parachuted behind Egyptian lines, then disobeyed orders to retreat. While winning the battle, he lost 41 of his troops.

Sharon had become a general by the 1967 Six Day War, in which Israel captured East Jerusalem, the West Bank and Gaza Strip, Sinai and the Golan Heights.

His most celebrated victory came in the 1973 Yom Kippur War. He launched a daring counterattack behind enemy lines to pin down the Egyptian army along the Suez Canal.

His status as a polarizing figure was cemented in 1982, when he was defense minister. To try to destroy the Palestine Liberation Organization, Sharon masterminded an invasion of southern Lebanon. An Israeli commission later held him indirectly responsible for the massacre of hundreds of Palestinian refugees by Lebanese militias.

Unbowed, Sharon continued to press hard-line policies in several other cabinet and parliamentary posts. As housing minister in the early 1990s, Sharon vastly expanded Israeli settlements in the occupied West Bank and Gaza Strip.

As an opposition member of parliament, he sharply criticized the 1993 Oslo Accords and the labor government's negotiations with Yasser Arafat and the Palestinians. Then in the fall of 2000, in what was widely seen as a provocative act, he visited the plaza in front of the Al Aqsa Mosque on the disputed Temple Mount in Jerusalem.

Within days, the so-called second intifada, or uprising, broke out with multiple Palestinian suicide bombings against Israeli civilians. In that political climate, Sharon won an overwhelming election victory to become prime minister in 2001.

The new prime minister refused to negotiate with Arafat, isolating him in Ramallah as Israel launched anti-terror military raids in the West Bank.

ARIEL SHARON: Yasser Arafat and the Palestinian Authority are returning to the belief that they can defeat Israel by means of armed struggle. They feel that violence will produce further Israeli concessions.

MARGARET WARNER: Sharon also pushed ahead with building a security fence to divide Israel and many settlements from the rest of the West Bank. And though Sharon has met with Arafat's successor, his decision to leave Gaza this summer was taken unilaterally.

Now Sharon is seeking a third term prime minister as head of new centrist party called National Responsibility.

MARGARET WARNER: So what drove Ariel Sharon's latest bold and surprising move? To explore that, we're joined by Martin Indyk, who dealt with Sharon frequently while serving as assistant secretary of state for near eastern affairs, and twice U.S. ambassador to Israel during the Clinton administration. He's now director of the Saban Center for Middle East Policy at the Brookings Institution in Washington. And Abraham Ben-zvi, an Israeli who is the Goldman visiting professor of government at Georgetown University, and professor of political science at Tel Aviv University in Israel. Welcome to you both.

MARGARET WARNER: Explain how this happened, why this happened, Martin Indyk. Here is this warrior politician who abandons the very successful and dominant right-wing party he founded to form a new one at the age of 77.

MARTIN INDYK: Well, I think that there is the immediate cause and the longer-term cause. The immediate cause is the fact that the Likud Party had become an impossible arena for him where he couldn't even get the appointment of his own ministers passed through the Knesset because there was such a strong opposition to him based on the fact that he had given up territory in Gaza. And that was the immediate cause.

The longer-term cause is that Sharon, coming to the end of his life, coming to the end of his political time, wants to, I think, fulfill what he sees as his historic responsibility to firm up, if not finalize, the borders of the Jewish state of Israel.

MARGARET WARNER: But does he think that forming a centrist party is more in tune with the public now than the Likud, which he led for all those years?

MARTIN INDYK: Both in tune with the public sentiment, which is to separate from the Palestinians, and in tune with what he considers necessary to do, which is to give up significant parts of the West Bank, something which the right-wing coalition that he had originally formed will not go along with.

MARGARET WARNER: Beyond the political calculations, professor, what would you point to in Sharon the man in a sort of deeper sense that might explain this?

ABRAHAM BEN-ZVI: Well, I think his current strategy is predicated very closely or is patterned closely on his modus operandi, both as a political leader and as a military leader. Basically Sharon is a man of action. And he's determined to preempt, to take the initiative in the same way that he was determined to take the initiative during the Yom Kippur War -- to initiate --

MARGARET WARNER: So in other words, militarily, he wants to do the same politically?

ABRAHAM BEN-ZVI: To outflank the opposition, ultimately to destroy the opposition -- outmaneuver, encircle the opposition. Here, I guess, first of all he was motivated in initiating the whole disengagement scheme by a desire to preempt a vacuum, a dangerous void and to perhaps preempt or abort an initiative by the quartet, by Europe, et cetera, which would have been detrimental to Israel to establish new facts on the ground.

Ultimately the tactic became a strategy; he became a legitimate figure worldwide, was, of course, accepted by Chirac and by the U.N., and I think, again, his final plan, his game plan right now, to take the initiative, after the election, to forge a coalition with the labor and to move, to delineate to, shape the parameters of permanent settlement. He will probably approach the Rubicon; he will not cross it.

MARGARET WARNER: But here is a man, Martin Indyk, who has been incredibly tough with the Palestinians politically and militarily all of these years. He now says he's forming a centrist party. Centrist in what sense, I mean, has he changed or has the center of gravity changed?

MARTIN INDYK: No he hasn't changed, as Abraham says. He's tactically very agile. So politically he's the most astute Israeli politician in terms of moving left or right with elegance in a way that enables him to go ahead with his purpose. And that hasn't changed.

I think people in Israel often say he's all tactics, no strategy. I don't think that's true of Sharon at all. He's always had a strategic vision. The strategic vision has changed a little bit as a result of the intifada and his understanding that the demographic threat to the Jewish state of Israel is at least as important as the conventional military threat and perhaps more so.

MARGARET WARNER: Meaning, in other words, that if they had held on to Gaza, essentially --

MARTIN INDYK: And the West Bank.

MARGARET WARNER: -- and the West Bank in toto, Israeli Jews would be completely outnumbered shortly by Palestinians.

MARTIN INDYK: Right. Exactly, within this decade; and he's come to understand that and understood politically that most Israelis have left not only Gaza but the West Bank in terms of their mental map. They want to separate from the Palestinians. They don't want to rule over them anymore. They want to get on with their lives. Sharon didn't want a fence, but that public sentiment led him as politician with his finger on the pulse of the people to build the fence, but where does he build the fence? Around the borders of what he would like to see as a robust Jewish state with Jerusalem in Israel's hands.

MARGARET WARNER: Undivided.

MARTIN INDYK: Undivided.

MARGARET WARNER: Have you seen an evolution in him?

ABRAHAM BEN-ZVI: Well, first of all, Sharon, there is no evolution in the sense that Sharon was never motivated exclusively or quintessentially by ideological considerations. He started his political career by forming a party which tilted to the left. He offered Yosi Sarid the number two position in his party. But basically he was motivated by instrumental considerations, but I think there were reinforcements --

MARGARET WARNER: Let me just explain for the American audience. When you say he was not ideological, you mean he's not really of the camp that thinks Israel must reclaim the entire biblical land of Israel?

ABRAHAM BEN-ZVI: Unlike Menachem Begin or Tak Shamile, he was more instrumental. Of course, the fact that he basically constrained them from the right --

MARGARET WARNER: Another Likud member.

ABRAHAM BEN-ZVI: It was part of his tactic. Basically outmaneuvering his opposition, outflanking his opposition, but it did not reflect a commitment to the greater land of Israel. And, of course, now when he gained legitimacy and public opinion by and large, except for hard-core Likud supporters, support overwhelmingly a massive withdrawal from the West Bank and 65 percent -- 68 percent of the Israeli population, public opinion supported disengagement. As a result, I think this is his legacy, his future commitment to try and accomplish perhaps another interim agreement.

MARGARET WARNER: Martin Indyk, you know this man. I mean, you've met with him many times. You've dealt with him. I think many people would say, you know, I'm 77 years old. I have had an incredible career. I have pulled off Gaza disengagement. There are another couple generations behind me. Maybe it's just time to go back to my farm. Why wouldn't he do that?

MARTIN INDYK: Because Sharon is very suspicious of the next generation, of the generation of baby Netanyahus and Ehud Baraks. He considers that he --

MARGARET WARNER: Two former prime ministers you just named.

MARTIN INDYK: To former prime ministers. He considers them highly irresponsible in the terms of the way they dealt with the Arabs and the issue of territory; he considers Shimon Peres, a leftist on the political spectrum, and Yitzhak Rabin, a centrist, as part of his generation, the warriors who fought for the independence of the state and who carry on their shoulders the responsibility for the future of the state. That generation, he said it at Rabin's 10th anniversary, at the cemetery last week, that that generation were the warriors who could, who understood what the Jewish state needed to survive.

So his last job, he sees I believe, is to ensure a robust Jewish state, which means to separate from the Palestinians with Jerusalem the spiritual religious center of Jewish life as the capital undivided, as you said. That's what he is trying to achieve; that's what he sees as his responsibility before he leaves office.

MARGARET WARNER: Do you agree that, for instance, the Palestinian, professor, should not be looking at, this Ariel Sharon forming a centrist party, with great elation. I mean, many Palestinians absolutely loathe this man, as we know; that he is not there to make peace in traditional terms.

ABRAHAM BEN-ZVI: That's an excellent point. But still I would say with guarded --

MARGARET WARNER: Would you agree with that point?

ABRAHAM BEN-ZVI: Yes, but with guarded optimism, yes, not with elation definitely, but I think Sharon will continue in a very Kissingerian tactic, namely piecemeal way, incremental change. I think he envisions after the election, hopefully he will form a coalition government with the labor. Another interim major Israeli withdrawal, perhaps seventeen, eighteen settlements from the West Bank and again shaping the future, delineated.

MARGARET WARNER: You're saying he could do this -- if he manages to win and head the government, he will be able to do it as head of this new party in a way he couldn't as head of Likud?

ABRAHAM BEN-ZVI: Of course. Because he could have definitely remained leader of Likud; he would have won probably the forthcoming primaries within Likud; he would have led his party to perhaps another four years of stagnation because the Likud Party would not permit Sharon to move. It would continue to humiliate, embarrass, constrain him.

And, as a result, the only way, and this is an indication, the fact that Sharon decide to defect to, break away from the Likud Party, which he formed 30 years ago, that's an indication that he's basically envisioning and he's planning, not improvising, a coalition with the labor election.

Of course, no single party would be able to rule exclusively with the coalition, jointly with the labor, to delineate the future. And the Palestinians have a reason for very guarded optimism perhaps.

MARGARET WARNER: Very briefly, based on your knowledge of this man, were you surprised by this move?

MARTIN INDYK: I was surprised because I thought that he would not leave the Likud, having built it up. It was an institutional base. He knew how important it was, as in effect the majority party in Israel -- that he would not easily walk away from it. He didn't easily walk away from it, but I think the critical point here is that he saw it now as a constraint on him that he could not achieve his life's purpose with the Likud, and he needed a new coalition. And to do it with the left is not unusual for Ariel Sharon -- in terms of joining with whatever force is necessary to achieve his vision.

Just on the Palestinians, they have reason to be concerned because he doesn't believe in the final agreement. He doesn't believe in peace. He believes in interim agreements negotiated with the United States, not with the Palestinians.

MARGARET WARNER: And creating facts on the ground. Thank you both.