How Libya reached its dangerous political impasse

TRIPOLI (Reuters) - Here is a timeline chronicling Libya's years of chaos and division:

2011 - Revolt and civil war

An uprising against Muammar Gaddafi's four-decade rule rapidly spreads, becoming an armed revolt aided by NATO air strikes. Gaddafi is ousted in August and killed in October.

2012 - Armed groups take root

A rebel council stages elections for an interim General National Congress which creates a transitional government but true power lies with an array of local armed groups.

Islamist militants gain ground and attack the U.S. consulate in Benghazi, killing the ambassador.

2013 - Growing divisions

Armed groups grow ever stronger, besieging government buildings and forcing the congress to bow to their demands. The body is divided and public trust is ebbing as it seeks to extend its 18-month term and delay elections.

Neighbouring Egypt, where the military has removed a Muslim Brotherhood government, is increasingly worried about militant groups in Libya and mistrustful of the Islamist-dominated congress.

2014 - East-west schism

Former army general Khalifa Haftar sets up a new Libyan National Army group that battles Islamist armed factions.

The congress rejects the results of an election for a new parliament - the House of Representatives (HoR) - and sets up a government that is backed by armed groups in the west.

Backed by Haftar, the newly elected parliament moves from Tripoli to the east in support of the previous caretaker government. Libya is now split between warring administrations in east and west.

2015 - Islamists on the march

Islamist groups take advantage of the chaos and Islamic State seizes the central city of Sirte in February. Militants also hold much of Benghazi and Derna.

In December, the warring parliamentary bodies sign the Libyan Political Agreement to set up a new transition under a Government of National Accord. The agreement confirms the HoR as Libya's parliament but gives members of the congress a new role as an advisory second chamber - the High State Council.

The agreement forms the basis for diplomacy for years to come, but on the ground the east and west remain divided.

2016 - Islamic State driven back

Despite the political agreement, the HoR rejects the new government as it takes office in Tripoli, entrenching Libya's east-west divide. Western armed factions eventually take Sirte from Islamic State as Haftar fights militants in Derna and Benghazi and seizes the energy-producing "oil crescent" region of central Libya.

2017-18 - Deepening chaos

Fighting intensifies as armed groups in the west battle for control of Tripoli while the eastern LNA and other major factions fight Islamist militant groups around the country. New peacemaking efforts quickly fall apart.

2019 - Haftar attacks Tripoli

After finally crushing Islamist groups in the east, Haftar drives his LNA through southern Libya, bringing most remaining oil fields under his control. In April, on the day the U.N. secretary general arrives in Tripoli for peace talks, Haftar launches a surprise offensive to capture the capital. His assault is backed by the UAE, Egypt and Russia.

Western Libyan armed groups come together to support the Tripoli government with help from Turkey, their alliance bolstered by a deal on maritime borders that angers Egypt and Greece.

2020 - Ceasefire

Turkey openly sends its troops to support Tripoli and Haftar's offensive collapses. As his forces pull back, evidence of atrocities is found in the town of Tarhuna. The sides agree a formal ceasefire and the U.N. convenes Libyan politicians and civil society in Tunis for a new peacemaking effort aimed at holding national elections the following year.

2021 - A failed election process

The eastern and western factions all accept a new Government of National Unity (GNU) meant to oversee elections in December. But the HoR in the east and the HSC in the west cannot agree on a new constitution or rules for the vote and the election falls apart at the last minute.

2022 - Standoff

Both parliamentary bodies now say the unity government has lost its legitimacy but the prime minister refuses to quit. The HoR in eastern Libya appoints a rival administration, but it fails to enter Tripoli, leaving the unity government still in control and the political standoff unresolved.

2023 - Paralysis

An uneasy peace prevails, but behind the scenes political factions continue to manoeuvre and the standoff continues. Diplomacy is focused on U.N. efforts to bring forward elections but many Libyans suspect their leaders are happy to avoid a vote that could push them from power.

In August, rival armed factions in Tripoli battle over the seizure of a commander.

(Reporting by Angus McDowall; Editing by Angus MacSwan)