Here is a breakdown of what caused the war and why it has so far proved impossible to stop.

THE HISTORY OF CONFLICT

Cameroon's political tensions date back 140 years. In 1884, Germany annexed Cameroon but lost it after World War I when it was partitioned between Britain and France.

The French part of Cameroon won independence in 1960 and was joined a year later by the smaller English-speaking British zone to the west, forming modern day Cameroon.

At the time, many in the British territory wanted to form their own state, but they were not given the option under a U.N.-officiated referendum. Secessionist sentiments have simmered ever since.

Despite the Anglophones' wealth of resources, including oil, cocoa and coffee, French-speaking politicians held sway. The Anglophones were forced to drive on the right hand side of the road and take on the CFA franc currency.

In 1972 President Ahmadou Ahidjo declared an end to federalism, erasing regional autonomy. His successor, current President Paul Biya, centralised things further when he came to power in 1982.

WHAT TRIGGERED FIGHTING IN 2017?

The separatist movement remained on the political fringe until late 2016, when English-speaking lawyers and teachers protested peacefully against having to work in French.

The government cracked down hard and civilians were killed in clashes with police. The crowds grew in response, and so did the violence. In October 2017, more than 20 were killed during marches, according to Amnesty International.

By mid-2017, many who had previously wanted just a return to federalism were calling for secession. Protesters waved the blue and white flag of Ambazonia - the separatists' proposed new state. An armed group called the Ambazonia Defence Forces began attacking government soldiers. Dozens of other groups have formed and carry out regular attacks on troops and civilians.

WHAT IS THE HUMAN AND ECONOMIC TOLL?

At least 6,000 people have died in fighting, according to the International Crisis Group. The U.N. estimates that over 700,000 people have been displaced. Both sides have been accused of abuses by human rights groups.

Separatists have enforced a boycott on schools, depriving 600,000 children of their education.

In 2019, the U.S. suspended Cameroon from its flagship trade initiative with Africa, AGOA, which gave it tariff-free access to the U.S. market, citing alleged human rights violations by Cameroonian security forces.

Two of the largest state-owned companies which produce crude, palm oil, banana and rubber have almost ground to a halt. Cocoa and coffee production has also been hit.

WHY HAVE PEACE EFFORTS STALLED?

In 2019, the government organised a national dialogue with opposition parties and other stakeholders but the main separatist leaders were absent.

Canada and Switzerland have initiated talks in recent years, which have fallen apart for lack of government or separatist participation.

One problem has been bringing together separatist groups who often work alone, with varying objectives. Some have called for the release of Anglophone political prisoners as a condition for talks, which Yaounde has refused.

(Reporting by Amindeh Blaise Atabong in Yaounde; Editing by Edward McAllister, Alexandra Hudson)

By Amindeh Blaise Atabong