WAR ON TERROR
On Oct 7, 2001, less than a month after the Sept 11 terror attacks, US President George W. Bush launches operation Enduring Freedom in Afghanistan, after the Taleban regime refuses to hand over Al-Qaeda chief Osama bin Laden.
In a matter of weeks, the US-led forces overthrow the Taleban, in power since 1996.
Attention is diverted from Afghanistan as US forces in 2003 mount an invasion of Iraq, which becomes the main US concern.
The Taleban and other Islamist factions regroup in their strongholds in southern and eastern Afghanistan, from where they can easily travel to and from Pakistan tribal zones.
PEAK OF 100,000 TROOPS In December 2009, President Barack Obama raises the strength of US forces in Afghanistan to around 100,000.
DEATH OF OSAMA
Osama, mastermind of the Sept 11 attacks that started the war, is killed on May 2, 2011, during an operation by US special forces in Pakistan, where he was in hiding.
END OF COMBAT OPERATIONS
In late December 2015, the Nato combat mission ends and is replaced by an assistance mission baptised Resolute Support.
However, the security situation degenerates. Amid a resurgent Taleban, on July 6 last year, Mr Obama again slows down the pace of withdrawal, saying that 8,400 US troops will remain in Afghanistan into 2017.
MEGA BOMB AGAINST ISIS
On April 13 this year, the US military drops the largest non-nuclear bomb it has ever used in combat, hitting Islamic State in Iraq and Syria (ISIS) positions in a network of tunnels and caves, killing 96 Islamists.
Last month, the American army kills ISIS' new leader in Afghanistan, the third such chief slain by Washington and Kabul.
On Monday, President Donald Trump cleared the way for the deployment of thousands more US troops to Afghanistan in his first formal address to the nation as commander-in-chief. Senior White House officials say he has authorised the Defence Secretary to deploy up to 3,900 more troops to Afghanistan.