It's three years since Britain withdrew all combat troops from Afghanistan after the end of Operation Herrick.
They'd been deployed over 12 years previously after the September 11 terrorist attacks of 2001 on New York's Twin Towers.
US intelligence quickly determined that the Islamist terror group al-Qaeda was responsible and the War in Afghanistan began.
Its leader, Osama bin Laden, and other key organisation figures such as Ayman al-Zawahiri, were in the country at the time.
Taliban leader Mullah Mohammed Omar demanded proof that bin Laden was involved in the terrorist attacks before handing him over to the US, and negotiations were attempted.
But the US rejected diplomacy, calling the overtures delaying tactics. So Operation Enduring Freedom commenced on October 7.
Despite the calls for evidence by the Taliban, bin Laden was guilty.
Two days prior to the September 11 attacks, a pre-emptive assassination of Afghan political and military leader Ahmad Shah Massoud, who rejected the Taliban's fundamentalist interpretation of Islam, had been carried out - probably by al-Qaeda.
It was aimed to shore up the Taliban's position in the event of US support for Massoud's Northern Alliance after 9/11.
However, the assassination did not prevent the overthrow of the Taliban.
The US and UK invaded Afghanistan and allied themselves with the Northern Alliance, with other nations such as France and Denmark joining the fight later on.
Together they forced the Taliban out of power, and Hamid Karzai became the new leader of the country.
From 2006, NATO forces in Afghanistan came under the umbrella of ISAF – the International Security Assistance Force.
Troops in Afghanistan increased from 1,300 in 2001 to 68,000 in 2009, with 36,000 of these US and 32,000 from NATO countries.
When Barack Obama became President, he placed General Stanley McChrystal in command, and it was McChrystal's assessment that more troops would be required to stop the resurgent Taliban from winning the war there.
The Taliban had become more organised and grown in strength financially, having taken donations from wealthy patrons in the Persian Gulf and by utilising poppies.
By 2006 90% of the global opium trade revolved around Afghanistan.
Attention had shifted to Iraq in 2002 and 2003, and now Obama was forced to escalate the war in Afghanistan. By the spring of 2010 over 1,000 US and 300 British troops had been killed.
Obama had approved the deployment of an additional 17,000 personnel in early 2009 and would add another 30,000 in 2010, as well as overseeing an increase in drone strikes in Pakistan.
In March 2010, Obama visited Afghanistan for the first time, telling President Karzai to clean up government corruption.
After the Navy SEAL raid that killed bin Laden in Abbottabad in 2011, Obama announced the planned withdrawal of 10,000 US troops by the end of the year and 23,000 more in 2012, in preparation for the complete departure of ISAF forces in 2014.
David Cameron also said British troop numbers would be drastically cut back.
This would end Operation Herrick, the term for British operations in Afghanistan from 2002 - 2014, while Operation Toral is the name for the current, lighter British involvement in Afghanistan.
453 British Armed Forces personnel had died (404 in combat) there between 2001 and 2015.
143,750 British personnel were deployed over the 14 years.
Sickness, wounds and psychological effects are estimated to have affected a quarter of those who served there.
Cover image: UK-US patrol in Sangin, 2007.