For the last two decades, the conflict in Afghanistan has made headline news around the world.
Britain entered Afghanistan with the US in 2001 and few then would have expected troops from both nations to still be in the country now in what has become America's longest war.
In the last 20 years, 150,610 UK personnel have served in Afghanistan.
The United States, meanwhile, says it wants all of its troops to have withdrawn by 11 September - the 20th anniversary of 9/11.
How did we get here?
After the 9/11 attacks in 2001, which killed almost 3,000 people in the US, American and British planes carried out air strikes in Afghanistan and began their assault on the Taliban.
The Taliban fled Kabul, the Afghan capital, in November 2001, leaving power.
In December of the same year, the UN established the International Security Assistance Force (ISAF).
ISAF was responsible for coordinating international military operations in Afghanistan and, in January 2002, the first contingent of ISAF peacekeepers arrived in the country.
The UK took on the first six-month rotation commanding the force and, by April 2002, there were 1,700 British troops in Afghanistan.
In 2003 the Taliban fought back and in August NATO took the lead on military operations.
Afghanistan became a priority for all NATO member and partner nations, and 130,000 troops from 50 NATO and partner nations were deployed in the country.
In January 2004, the UK saw its first combat casualty when a British soldier was killed in a suspected suicide attack.
November of the same year saw Hamid Karzai elected as the first president of Afghanistan since the fall of the Taliban.
In February 2006, British troops moved into Helmand Province, where Camp Bastion was built.
Before the end of the year, 21 UK troops had been killed on operations in Helmand.
Another 14 died when an RAF Nimrod plane crashed in Kandahar province – the biggest single loss of life for British forces since the Falklands War in 1982.
In July 2006, the mission in Afghanistan changed from a peacekeeping operation to a combat mission.
2009 marked the UK's deadliest year in the country, with 108 service personnel killed.
UK forces reached their peak in 2010 with more than 10,000 troops deployed in the country.
Operation Moshtarak also saw the largest joint offensive between US and UK troops, with 15,000 personnel pushing out the Taliban from Helmand strongholds.
In July 2010, the UN and the Afghan government agreed that there would be a transition that sees Afghanistan lead security, with the change in command beginning in January 2011.
On 26 October 2014, British troops ended their combat role in Afghanistan.
A ceremony in December 2014 marked ISAF's formal completion of its mission in the country, concluding the three-year transition process.
In January 2015, the NATO-led Resolute Support Mission (RSM) was launched to train, advise and assist the Afghan security forces – a mission British troops continue to assist with.
In January 2018, NATO committed to sustaining RSM until conditions indicated a change was appropriate.
Financial support was also extended to Afghan security forces until 2024.
In February 2020, the US and Taliban signed a peace deal that included a conditions-based agreement for international troops to leave Afghanistan by May 2021.
More than 450 British personnel have died in Afghanistan since the start of operations in 2001.