In the mid-thirties Begin received a law degree. In 1938 he became head of Betar Poland, a 70,000-member organization that formed part of the national movement founded by Jabotinsky. Begin concentrated on military training, foreseeing the need to defend Polish Jewry. At the outbreak of World War II he fled to Vilna, was arrested in 1940 by the NKVD (a forerunner of the KGB) and was sentenced to eight years in a labor camp in Siberia. He was freed in 1941 because of his Polish citizenship and joined the Free Polish Army, which in 1943 made its way to the Middle East.

Contacting the dormant underground organization of the national movement - the Irgun Tzeva'i Le'umi (Etzel) - Begin set about revitalizing it. In 1944, when the magnitude of the Holocaust became evident, the Etzel broke away from the mainstream Zionist policy of restraint. Under Begin's leadership the pace and the scope of Etzel's challenges to British rule increased, and after the war he ordered many of Etzel's operations, including the Akko prison breakout and the destruction of the British administration's central offices located at the King David Hotel in Jerusalem. The growing militancy of Etzel's operations brought Begin into conflict with the mainstream Zionist strategy of Ben-Gurion - causing an ideological-political rift and personal rancor between the two leaders which lasted for many years. After the establishment of the Israel Defense Forces (IDF) by the Provisional Government in June 1948, the two dissident military organizations (the Etzel and the Lehi) were disbanded and their members absorbed into the IDF.

Menachem Begin turned to parliamentary politics, founding the Herut Party, which was based on the political ideology of his mentor, Ze'ev Jabotinsky. As a Member of Knesset, he dominated the political opposition to the ruling Labor party's hegemony during the first three decades of independent Israel.

During his years as leader of the right-wing opposition, Begin, a gifted and charismatic orator, gave expression to his disapproval of government policy not only in parliament, but also at public demonstrations. In the 1950s he led the movement against the reparations agreement with West Germany, and after the Sinai campaign of 1956 - the opposition against withdrawal from Sinai. In 1965, Begin merged his Herut party with a liberal party, a merger which served as the foundation of the future Likud party.

Two years later the crisis prior to the outbreak of the 1967 Six-Day War led to the formation of a national unity government, of which Begin became a member. For almost three years he was part of the decision-making body, until disagreement over an American peace initiative (the Rogers Plan) prompted him to resign.

In the 1977 elections, Begin's Likud party gained 43 Knesset seats, compared to the Labor Alignment's 32. Menachem Begin became Prime Minister, serving for six and a half years - from the spring of 1977 to the fall of 1983.

His leadership style - with more formal attire, and emphasis on ceremonial aspects of the government - was markedly different from the "open-shirt" approach of his predecessors. In domestic affairs, Begin redirected priorities, channeling more national resources into development programs such as Project Renewal, which was responsible for the rehabilitation of distressed neighborhoods and development towns. After thirty years of Labor party rule, his party also sought, albeit with little success, to ease centralization and to liberalize the economy. He also intensified the national campaign for the right of Soviet Jews' repatriation in Israel and he gave the orders for the evacuation of the Ethiopian Jewish community, which only took place some years later.

Prime Minister Begin's most outstanding achievement was the signing of the Peace Treaty with Egypt. In November 1977, six months after Begin became Prime Minister, President Anwar Sadat of Egypt came to Jerusalem. This visit inaugurated two years of negotiations that culminated in the Camp David Accords , which called for Israel's withdrawal from Sinai and the establishment of Palestinian autonomy, in exchange for peace and normal relations with Egypt. A Treaty of Peace terminating the state of war between the two countries was signed in 1979. Prime Minister Begin and President Sadat were awarded the 1978 Nobel Peace Prize for this achievement. In the spring of 1982, despite widespread protest in Israel, Begin - who put much store in legal documents - withdrew from Sinai, including the town of Yamit and the other Jewish settlements.

In 1981 Begin ordered the Israel Air Force to destroy the nuclear reactor in Osirak near Baghdad, Iraq, shortly before it was to become operative. The wisdom of this decision and its successful execution, which were condemned by the international community at the time, became fully apparent a decade later - in the 1991 Gulf War.

Twice during Begin's tenure as Prime Minister, military actions were launched in response to Palestinian terrorist acts against Israeli citizens from Lebanese territory: the 1978 "Operation Litani" and the 1982 "Operation Peace for Galilee". Both operations were aimed at dislodging the PLO from southern Lebanon. The 1982 Operation grew into a protracted conflict with complex ramifications and a considerable number of casualties.

The strains of office, failing health and the death of his wife caused Menachem Begin to resign from his post in September 1983 and to retire to the seclusion of his home. He died in March 1992, at the age of 79.