Under his command, the army, allied with the Lebanese Forces, clashed with Jammoul, a Syrian-backed alliance led by the Druze Walid Jumblatt, in what is known as the Mountain War.

By the end of the conflict, the government suffered heavy defeat, and lost control over wide areas of Mount Lebanon.

As a result of heavy pressure, and the withdrawal of the multinational forces, Gemayel visited Damascus in 1984, and formed a national unity government, including members from the opposition, headed by Rashid Karami.

In 1986, he helped Samir Geagea organize a coup against the leader of the Lebanese Forces Elie Hobeika, for signing the Tripartite Accord with Berri and Jumblatt.

His grandfather was forced to leave Lebanon in the early 20th century as a result of his opposition to the Ottoman Empire and therefore, had to spend several years living in Egypt.

Gemayel's great uncle, Antoine, traveled to the Paris Peace Conference in 1919 as a political representative of the Maronite Christian community in Lebanon.

[4] In a 1970 by-election, he was elected to succeed his deceased uncle, Maurice Gemayel, as a member of the National Assembly; he defeated Fuad Lahoud by a margin of 54% to 41%.

[citation needed] When Bashir Gemayel was assassinated by a member of the Syrian Social Nationalist Party, therefore, Amine was regarded as a natural choice to bring together both the supporters of his slain brother, and his Muslim opponents.

From 1990 to 30 July 2000, he resided in Paris as an exiled leader of the opposition, and lectured extensively on Lebanon and the Middle East in various countries worldwide.

[citation needed] Many criticized Gemayel for not moving decisively enough to assert the authority of the government, but others have pointed out that with most of the country under foreign occupation, there was little that he could do.

When Amine Gemayel took office, Lebanon was torn by Israel's invasion of June 1982, and its subsequent occupation of large areas of Lebanese territory.

In 1984, Amine Gemayel dissolved the "Arab Deterrence Force", which provided the legal framework for Syria's military presence since 1976;[3] and in 1985, he refused to ratify the so-called "Damascus Agreement" brokered by the Syrian government between the fending Lebanese chiefs of militias, which aimed at disintegrating any independent decision-making process in Lebanon.

In 1987, he promulgated the law annulling the "Cairo Agreement" of 1969, which authorized the PLO to use Lebanon as a base for military operations against Israel, disregarding Lebanese sovereignty.

Officials also held then Army Commander General Ibrahim Tannous responsible for “neglect” because an illegal military deal was sealed during his term of office.

This was all brought up in 2002 as part of investigations by a special parliamentary committee into former President Amin Gemayel's role in the Puma aircraft sale.

[9] He also founded "Beit-al-Mustakbal", (the house of the future), a think-tank and research center which published Haliyyat, a quarterly journal edited in Arabic, French and English, comprising a chronology of the main events in the area, press reports, and a series of essays.

On 30 July 2000, however, he returned to Lebanon[11] and began to organize the opposition to the government of President Émile Lahoud, whom he regarded as a Syrian puppet.

[13] Although his efforts to forestall the ensuing Iraq War were not successful, they fuelled speculation that he might be a candidate for Secretary General of the United Nations when Kofi Annan's term expired.

Amine lost by a small margin to an unknown candidate presented by Michel Aoun as a member of the Free Patriotic Movement.