Hezbollah - or the Party of God - is a powerful political and military organisation in Lebanon made up mainly of Shia Muslims.
It emerged with financial backing from Iran in the early 1980s and began a struggle to drive Israeli troops from Lebanon.
Hostility to Israel has remained the party's defining platform since May 2000, when the last Israeli troops left Lebanon due in large part to the success of Hezbollah's military arm, the Islamic Resistance.
Hezbollah's popularity peaked in the 2000s, but took a massive dent among pro-Western Lebanese people when it was at the centre of a huge, destructive war with Israel following the capture of two Israeli soldiers in 2006.
Hezbollah is the strongest member of Lebanon's pro-Syrian opposition bloc which has been pitted against the pro-Western government led by Saad Hariri.
It has several seats in parliament and has ministers in a national unity government formed in late 2009.
It also blocked the election of a new president by repeatedly boycotting sessions of parliament.
The stalemate ended on 21 May 2008, when the group reached a deal with the government under which its power of veto was recognised.
Washington has long branded Hezbollah a terrorist organisation and has accused it of destabilising Lebanon in the wake of Syria's withdrawal of its troops from the country following the assassination of former Lebanese Prime Minister Rafik Hariri.
The movement long operated with neighbouring Syria's blessing, protecting its interests in Lebanon and serving as a card for Damascus to play in its own confrontation with Israel over the occupation of the Golan Heights.
Hezbollah leaders have continued to profess its support for Syria, while stressing Lebanese unity by arguing against "Western interference" in the country.
As well as a political clout, Hezbollah has wide popular appeal by providing social services and health care. It also has an influential TV station, al-Manar.
Hezbollah's biggest test came in mid-2006, when its fighters captured two Israeli soldiers in a cross-border attack, killing a number of others.
The incident triggered a fierce month-long war with Israel, which ended in a ceasefire.
Having survived a massive military onslaught, Hezbollah declared victory, enhancing its reputation among many in the Arab world.
Its critics, however, blamed it for provoking the massive destruction which Israel wreaked in Lebanon.
Despite two UN resolutions (1559 passed in 2004, and 1701, which halted the war) calling for disarming of militias in Lebanon, Hezbollah's military arm remains intact.
Hezbollah was conceived in 1982 by a group of Muslim clerics after the Israeli invasion of Lebanon.
It was close to a contingent of some 2,000 Iranian Revolutionary guards, based in Lebanon's Bekaa Valley, which had been sent to the country to aid the resistance against Israel.
Hezbollah was formed primarily to offer resistance to the Israeli occupation.
It also initially dreamed of transforming Lebanon's multi-confessional state into an Iranian-style Islamic state, although this idea was later abandoned in favour of a more inclusive approach that has survived to this day.
The party's rhetoric calls for the destruction of the state of Israel. It views the Jewish state as occupied Muslim land and it argues that Israel has no right to exist.
The party was long supported by Iran, which provided it with arms and money.
Passionate and demanding
Hezbollah also adopted the tactic of taking Western hostages, through a number of freelance hostage taking cells.
In 1983, militants who went on to become members of Hezbollah are thought to have planned a suicide bombing attack that killed 241 US marines in Beirut.
Hezbollah has always sought to further an Islamic way of life. In the early days, its leaders imposed strict codes of Islamic behaviour on towns and villages in the south of the country - a move that was not universally popular with the region's citizens.
But the party emphasises that its Islamic vision should not be interpreted as an intention to impose an Islamic society on the Lebanese.