On the day after Israel had proclaimed its independence in 1948, a short, spare man with a reputation for engineering spectacular acts of terrorist violence turned to the radio with a message embodying his zionist beliefs.

"It is Hebrew arms which decide the boundaries of the Hebrew state. So it is now in this battle; so it well be in the future." Menahem Begin declared as Arab armies converged on the new Israel nation. "Whoever does not recognize our natural right to our entire homeland does not recognize our right to any part of it. And we shall never forgo this natural right."

Twenty-nine years later, Begin has exchanged his role as underground commander for Israel's top political office. Yet much of the daring, resoluteness and dramatic flare displayed in his earlier years have stayed with him. Begin, now master of the daring act, has become the first Israeli prime minister to welcome an Arab head of state to his jewish homeland.

As it was nearly three decades ago, the radio has remained a touchstone of Begin's political drama. Although his message was no longer 3 call to battle, Begin broadcast this month an extraordinary plea to the Egyptian people, in which he quoted from the Koran and appealed for an end to war and bloodshed. His message was one in a series of steps that led to Egyptian President Anwar Sadat's arrival in Israel yesterday.

Throughout Israel's 29 years. Begin has remained a spokesman for the political right, a hard-liner who opposed concessions to the Arabs. Again and again he was on the attack against more conciliatory Israeli politicians. When a Cabinet was formed in 1974, Begin complained, "We have not seen such a collection of doves since the days of Noah's Ark."

Begin's adamant stand, nevertheless, has been cited since his victory in last May's elections as offering at least some hope of moves toward an Arab-Israeli settlement. An analogy has repeatedly been drawn with the achievement of a U.S. hard-liner, former President Nixon, in opening doors to China.

Because of his unyielding Zionist fundamentalism, Begin has been viewed as one of the few Israeli politicians who could make concessions to the Arabs without losing Israelis' support.

Begin, now 64, commanded the underground Irgun Zvai Leumi (National Military Organization) in the 1940s during the time of its most spectacular - and often widely condemned - undertakings. These included blowing up a wing of the King David Hotel in Jerusalem in 1946, causing 91 deaths. Sadat is now staying at the same hotel. Irgun raiders also took part in what later became known as the 1948 "massacre" at the Arab village of Deir Yassin, in which 250 Arabs were killed.

When Begin's rightist Likud aliance came to power in May's parliamentary elections, the victory marked a major political shift. Begin's bloc unexpectedly toppled the Labor Party, which had dominated Israel since independence, amid discontent over Labor scandals and inflation.

A baldish figure in horn-rimmed glasses, Begin is gracious, friendly and gentle. His demeanor contrasts sharply with his harsh reputation as a terrorist leader, a description he has always rejected. He considers himself, instead, to have been an Irgun freedom fighter.

A man of courtly manner, Begin often bows and kisses women on the hand. In a nation when most men go about in shirt sleeves, Begin usually wears a jacket and tie. Even his close associates call him "Mr Begin."

He has long been a spellbinding orator, whose rhetoric is sometimes punctuated with biting sarcasm. Before he became prime minister this year, Begin had spent 29 years in the Knesset, Israel's parliament, where he was customarily a dissident - often bitterly at odds with government leaders.

Recently, Begin's health has become a recurring problem. He suffered a severe heart attack last March. A few days after the May elections, he was hospitalized for what was termed exhaustion. On Sept. 30 he was described as an inflammation of the membrane surrounding his heart.

Begin's deeply held Zionist beliefs appear to have formed in his earliest years.

Menahem Wolfovitch Begin was born Aug. 16, 1973, in Brest-Litovsk, Poland, now the Soviet city of Brest. His parents, he later wrote, were murdered by the Nazis during World War II. He attended a religious Zionist Hebrew school and the Polish high school and studied law at Warsaw University.

At 16, Begin joined the Betar, a militant youth movement affiliated with the World Union of Revisionist Zionists, which advocated a Jewish state in Palestine. He became head of the Betar movement in Poland in 1939.

At the outbreak of World War II, Begin was arrested by Soviet authorities in Soviet occupied Vilna and was imprisoned in concentrations camps in Siberia and elsewhere. He spent seven days in solitary confinement - an experience which, he later said, taught him a lesson in human endurance.

Released from prison in 1941, Begin joined the newly organized Polish exile army of Gen. Wladyslaw Anders and went with it to the Middle East, arriving in Palestine in May 1942. His wife, Aliza, was already there.

In 1943, Begin became commander of the Irgun - a small, tightly organized force that carried out surreptitious raids, bombings and other violent acts designed to help dislodge the British from Palestine and establish a Jewish nation. Begin and his Irgun followers were repeatedly in disagreement with more moderate Zionist leaders.

Begin lived in secrecy, using assumed names and disguising himself for a time by wearing a beard. A reward of 10,000 British pounds was offered for information leading to his arrest. From his account in his book of memoirs, "The Revolt," Begin appears to have been a planner, organizer and strategist, seldom participating directly in an Irgun raid.

After independence, Begin formed the Herut Party, which later merged with other parties to form the Likud, now the country's principal right-wing alliance.

Only once before he become prime minister was Begin brought into an Israeli government. In 1967, before the start of the six-day Arab-Israeli war, he was made minister without portfolio in what was intended as a national unity government. He resigned three years later in protest against Israel's acceptance of an American proposal that called for Israeli withdrawal from occupied Arab territories.