As Israeli fighter-bombers lifted off the runway at the Etzion air base on the edge of the Sinai Peninsula last Sunday and headed toward the Saudi Arabian desert and Iraq, Prime Minister Menachem Begin summoned his 15 Cabinet ministers to his house in the fashionable Rehavia section of Jerusalem.

Because secrecy was vital to the success of the mission, Begin told each minister he was wanted alone for a private discussion on an absolutely confidential topic and that a helicopter would be sent for him.

The ministers were puzzled as they headed for Begin's home. Religious Affairs Minister Aharon Abu-Hatzeria, acquitted recently of corruption charges, thought Begin was going to ask for his resignation. Interior Minister Yosef Burg, of the pivotal National Religious Party, thought Begin might want to make an importnat coalition proposal. Other minisers though something big was up on the Syrian missile crisis.

As they walked into the prime minister's living room, each was startled to see his assembled colleagues there. "Their mouths dropped. It was like a 'This Is Your Life' show," an aide to Begin said.

Then, in somber tones, Begin told his ministers that Israeli Air Force jets were on their way to bomb Iraq's French-built, 70-megawatt nuclear reactor near Baghdad. It was a dangerous mission, he said, and one which would be certain to create a firestorm of world reaction against Israel.

The ministers waited tensely, drinking tea and talking among themselves while Begin talked by telephone with the Israeli defense forces headquarters in Tel Aviv, which was in direct radio contact with the attacking planes. Then, shortly after 5:30 p.m., the news came: The planes had destroyed the reactor and were on their way home. The mission, Begin said, had been "carried out to perfection."

There were no celebrations or toasting, participants said, and the ministers quietly left for their own homes, each reflecting on the enormous political ramifications of the first major military action by any country against a nuclear installation.

The Cabinet had decided that Israel would make no announcement about the raid until it was disclosed by Iraq or elsewhere in the Arab world. That decision was in keeping with Israeli policy on major covert military actions, and the ministers felt that Iraqi President Saddam Hussein might be so humiliated by the attack that he would attempt to cover it up.

Hussein, who reportedly was visiting the front in the war with Iran, said nothing of the strike for 24 hours. Iraq's ambassador to Rome slaid in a press conference Thursday that Iraq did not know where the attacking planes came from at first.

But when Radio Jordan broadcast the news at 2 p.m. Monday, Begin ordered his press aide, Uri Porat, to make it public here. Porat called Israel's radio, but because the astonished editors there at first thought a hoaxer may have been posing as Porat, the bulletin was delayed an hour. When Begin turned on the 3 p.m. news in Hebrew and heard nothing about the raid, he had Porat call the radio station and demand an explanation.

Begin called the go-ahead signal for the raid one of his most difficult decisions, one that followed what he called a two-year "nightmare" of thinking about an atomic explosion over Tel Aviv.

Actually, the Israeli Cabinet made the decision in principle at a Cabinet meeting in October. Since the attack, officials have made clear that Begin proposed it at that time and no one voted against it.

Several times the hour was fixed for launching the mission, only to be postponed by Begin. When the attack was set for May 10, the prime minister halted it after receiving on the same day an urgent, handwritten appeal from opposition Labor Party leader Shimon Peres urging Begin in coded phrases to postpone the strike and try diplomacy instead.

Since the raid, Begin's motive for timing it as he did has been clouded by charges arising out of the tempo of a heated political campaign for the June 30 national election.

Begin insists that the Iraqui reactor would have become "hot," with the placing of enriched uranium in its core early next month, and that bombing it after that would have set off a chain reaction that would scatter deadly radioactivity over densely populated Baghdad.

Peres, who in his May 10 letter warned Begin that "Israel would be like a tree in the desert," maintains that even though Iraq was pushing the French to have the reactor operatinal by early July, neclear experts said it was doubtful it could have been complete before Sept. 1.

Instead of bombing now, Peres says, Israel should have spent another month or two seeking to convince newly elected French President Francois Metterrand that an Iraqi atomic bomb would be a threat to world peace. Metterrand, who earlier had indicated misgivings about France's reactor sale to Iraq, might have been able to exchange Iraq's 93 percent enriched fissionable uranium for a different uranium that could not be used in a bomb, Peres said.

Peres charges that Begin put electoral interests ahead of national interests and ordered the bombing Sunday to take advantage of a predictable upsurge in popular support during the last weeks of the election campaign.

If that was Begin's thinking -- and there is no proof that the timing of the raid was motivated primarily by electoral considerations -- then it has had the intended effect.

Overwhelming Israel public support for the bombing, coupled with the worldwide condemnation of israel for pursuing a Middle East monopoly on nuclear arms, appears to have propelled Begin further ahead in his quest for reelection.

The most recent poll prior to the raid, conducted by the Applied Research Center and published yesterday in the Jerusalem Post, indicates that Begin's ruling Likud bloc stands to win up to 46 seats in the 120-member parliament, enough to form a coalition. Labor would get 40 seats, according to the poll.

While no polls have been completed since the bombing, one of Israel's most respected public opinion analysts, Hanoc Smith, said yesterday that he felt the impact of the raid while sampling opinion throughout Israel during the last several days for a poll to be issued next week.

"I got the effects of it, and it's very favorable for Begin. There is no question that the Likud will pick up considerably as a result of the Iraq operation," Smith said.

According to informed Israeli sources, Begin and his senior advisers talked at length on numerous occasions about the likely world reaction to the bombing mission, particularly the reaction from the United States. Begin, it is understood, was warned that the air strike could result in a suspension of U.S. arms shipments to Israel and that it might tip the balance against Israel on the proposed sale of U.S. radar sentry planes to Saudi Arabia, over whose territory the Israelis would have to fly.

But Begin is said to have told his aides he thought negative reaction would only be temporary.

Begin said, "I believe that the nations are with us. But if, for various reasons which I do not want to go into, several governments condemn us, and they may repeat it in the Security Council, well, my friends, what can we do? We are an ancient people. We are used to it. We survived, we shall survive, and a comdemnation, if it is unjust, can be condemned."

The potential impact of the raid on the outcome of the election may explain the extraordinary flurry of public statements by Begin about the details of the bombing and the condemnations by foreign governments.

"He's making a virtue out of a necessity," one of his aides said, adding "Find me one Israeli on the street who thinks that that reactor should still be there."

"What is his next surprise?" a seemingly dispirited Peres asked bitterly at a press conference on Wednesday.