In April last year, Sudan was thrown into disarray when its army and a powerful paramilitary group began a vicious struggle for power.

The war, which continues to this day, has claimed more than 15,000 lives. And in what the United Nations has called one of the world's "largest displacement crises", about nine million people have been forced to flee their homes.

There have been warnings of genocide regarding the western region of Darfur, where residents say they have been targeted by fighters based on their ethnicity.

Here is what you need to know.

Sudan is in north-east Africa and is one of the largest countries on the continent, covering 1.9 million sq km (734,000 sq miles).

The population of Sudan is predominantly Muslim and the country's official languages are Arabic and English.

Even before the war started, Sudan was one the poorest countries in the world. Its 46 million people were in 2022 living on an average annual income of $750 (£600) a head.

The conflict has made things much worse. Last year, the economy shrunk by 40%, Sudan's finance minister said.

After the 2021 coup, a council of generals ran Sudan, led by the two military men at the centre of this dispute:

They disagreed on the direction the country was going in and the proposed move towards civilian rule.

The main sticking points were plans to include the 100,000-strong RSF into the army, and who would then lead the new force.

The suspicions were that both generals wanted to hang on to their positions of power, unwilling to lose wealth and influence.

The RSF was formed in 2013 and has its origins in the notorious Janjaweed militia that brutally fought rebels in Darfur, where they were accused of ethnic cleansing against the region's non-Arabic population.

Since then, Gen Dagalo has built a powerful force that has intervened in conflicts in Yemen and Libya. He has also developed economic interests including controlling some of Sudan's gold mines.

Before the current conflict erupted, the RSF had been accused of human rights abuses, including the massacre of more than 120 protesters in June 2019.

Such a strong force outside the army has been seen as a source of instability in the country.

Shooting between the two sides began on 15 April 2023 following days of tension as members of the RSF were redeployed around the country in a move that the army saw as a threat.

There had been some hope that talks could resolve the situation but these never happened.

It is disputed who fired the first shot but the fighting swiftly escalated in different parts of the country.

This fighting is the latest episode in bouts of tension that followed the 2019 ousting of long-serving President Omar al-Bashir, who came to power in a coup in 1989.

There were huge street protests calling for an end to his near-three decade rule and the army mounted a coup to get rid of him.

But civilians continued to campaign for the introduction of democracy.

A joint military-civilian government was then established but that was overthrown in another coup in October 2021, when Gen Burhan took over.

And since then the rivalry between Gen Burhan and Gen Dagalo has intensified.

A framework deal to put power back in the hands of civilians was agreed in December 2022 but talks to finalise the details failed.

When it began, the conflict appeared to be around the control of key installations.

However, much of it is now happening in urban areas and civilians have become unwitting victims.

The RSF captured much of the capital, Khartoum, and Darfur.

The military controls most of the north and the east, including the key Red Sea port of Port Sudan.

In a major blow to the army, the RSF seized the strategic city of Wad Madani in December, along with much of the surrounding Gezira state. Hundreds and thousands of civilians were forced to flee the city, which had become a hub for humanitarian services and a refuge for those who had escaped conflict in other parts of the country.

In February, the army recaptured the centre of Omdurman, one of three cities along the River Nile that form Sudan's wider capital, Khartoum. It regained control of the state broadcaster there - a symbolic breakthrough for the army.

Attention is now on el-Fasher, the last major urban centre in Darfur that is still held by the army. The RSF has laid siege to the city, causing hundreds of casualties, overwhelming hospitals and blocking food supplies.

As well as sparking major displacement, both sides in the conflict have been accused of war crimes.

When leaving his post in September, UN envoy to Sudan Volker Perthes accused the RSF of committing sexual violence, looting and killings in areas it controls. He also condemned the Sudanese armed forces for indiscriminate aerial bombings.

During the early days of the war, the BBC found that both sides had launched airstrikes and artillery fire at hospitals while patients were still in the building and doctors have also been singled out for attack. Both acts are potential war crimes.

The UN says the war has triggered the "world's worst hunger crisis". According to non-profit organisation Action Against Hunger, five million Sudanese people are dealing with "emergency levels of hunger".

Aid agencies have long complained that security threats and roadblocks have greatly hampered their effort to deliver vital goods, like food, to the people who need them.

In October, the BBC saw fresh evidence of ethnic cleansing in Darfur, most of which has been blamed on militias that are part of - or affiliated with - the RSF.

This year a report from campaign group Human Rights Watch said ethnic cleansing and crimes against humanity had been committed against ethnic Massalit and non-Arab communities in the region by the paramilitary forces and its Arab allies.

The UK, UN, US and a number of other entities have said civilians in the state are being targeted because of their identity.

UN genocide expert Alice Wairimu Nderitu told the BBC Darfur was facing a growing risk of genocide as the world's attention remained focused on conflicts in Ukraine and Gaza.

The current violence has erupted out of a long history of tensions over resources between non-Arab farming communities and Arab pastoralist communities.

The RSF emerged from the Janjaweed militia, which was accused of genocide and ethnic cleansing against non-Arab communities in Darfur in 2003, after rebels took up arms, accusing the government of ignoring the region.

The RSF denies responsibility for recent ethnic cleansing in Darfur, saying it is not involved in what it describes as a "tribal conflict".

The UN and other major humanitarian groups have issued several dire warnings about the situation in Sudan, accusing the international community of "forgetting" the African country.

For instance, International Crisis Group has called diplomatic efforts to end the war "lacklustre", while Amnesty International labelled the world's response "woefully inadequate".

Some international bodies have allocated funding to Sudan since the war started. In April, French President Emmanuel Macron announced a €2bn ($2.1bn; £1.7bn) aid pledge from the international community.

Foreign countries have also attempted to organise negotiations between the army and RSF. There have been several rounds of peace talks in Saudi Arabia and Bahrain - but all have failed.

The African Union and UN have a shared priority - to establish a ceasefire and bring the army and the RSF together.

BBC News deputy Africa editor Anne Soy reports that both sides, especially the army, have shown an unwillingness to work towards these goals.

At the end of May, the US's request that the army return to peace talks was denied in firm terms.

According to Reuters news agency, UN experts say the RSF has been backed by neighbouring African states including Chad, Libya and South Sudan throughout the war.

The United Arab Emirates (UAE) has been accused of arming the RSF, but the Gulf nation has denied any involvement.

This year, both the UK and the US singled out the UAE in separate appeals for outside countries to stop backing Sudan's warring parties.

There are also reports that Iranian-made armed drones have helped the army regain territory around Khartoum.