According to a recent UN report, over 3,000 Afghan civilians were killed in the first half of 2019.
Following the 9/11 terror attacks in the United States which claimed the lives of around 3,000 people, the US intervened in Afghanistan to rid Al-Qaeda of its sanctuaries.
The US war on terror operation opened a military front in Afghanistan.
Less than a month after the September 11, 2001 attacks in New York and Washington -- President George W. Bush launched an operation "Enduring Freedom" in Afghan.
Within weeks US-led forces overthrew the Taliban which was in power since 1996.
Afghanistan's fundamentalist Taliban regime had been sheltering Osama bin Laden and his Al-Qaeda movement who were accused of the attacks on the US.
Within months after the attack, the US had placed around 1,000 American soldiers on the ground by November 2001. The number rose to 10,000 the next year.
In 2008, the US command in Afghanistan called for more manpower. The then-president Bush sent additional soldiers and about 48,500 US troops were deployed.
Under Barack Obama, the number further rose to 68,000. By 2012 more than 1,50,000 foreign soldiers were deployed in Afghanistan, of which 100,000 were American.
The US special forces operation in Pakistan killed Bin Laden on May 2, 2011.
Though the NATO alliance ended its combat mission in Afghanistan on December 31, 2014. But 12,500 foreign soldiers -- of which 9,800 were American -- remained in Afghanistan to train the country's troops and conduct anti-terrorist operations.
Over the years security in Afghanistan degenerated as the Taliban's insurgency expanded, with the Islamic State (IS) group also becoming active in early 2015.
Consequently, in July 2016, Obama also slowed the planned pace of withdrawal of US troops, saying 8,400 will remain into 2017.
In August 2017, the new US President Donald Trump re-committed thousands of more soldiers. In mid-November, some 3,000 soldiers arrived to reinforce the 11,000 troops already deployed.
The true cost of the war is borne by the Afghan civilians who died in huge numbers since the war on terror started.
According to a recent UN report, over 3,000 Afghan civilians were killed in the first half of 2019. The report titled, "UN Assistance Mission in Afghanistan" said at least 3,812 Afghan civilians were killed or wounded in the war against Taliban.
The report further added that more civilian deaths had occurred due to forces than by the Taliban and other militants. The report refers to deaths caused during Afghan and US military operations such as airstrikes against insurgents.
A UN report in February 2019 said more than 32,000 civilians had died, BBC reported.
Al-Qaeda hijacked a total of four planes. The third hit the Pentagon and the fourth, Flight 93, crashed in a field in Shanksville, Pennsylvania.
In addition to those killed on September 11, thousands of first responders, construction workers and residents have since developed illness, many of them terminal, as a result of inhaling the toxic fumes.
New York honored Wednesday the almost 3,000 people killed on September 11, 2001 in a solemn ceremony at Ground Zero where hijacked Al-Qaeda planes brought down the Twin Towers.
Relatives of victims, police officers, firefighters and city leaders gathered at the National September 11 Memorial to mark the 18th anniversary of the deadliest single attack on US soil.
They held poignant moments of silence at 8:46 am (1246 GMT) and 9:03 am, the precise times that the passenger jets struck the North and South Towers.
New York Governor Andrew Cuomo, Mayor Bill de Blasio, and his predecessors Michael Bloomberg and Rudy Giuliani were among those who attended.
In what has become an annual tradition, relatives began reading out the long list of those who were killed, saying a few words about those who died, in a ceremony that takes almost four hours.
"We love you, we miss you and you will always be America's heroes," said one woman after reading out the names of her brother and cousin.
Relatives hugged and consoled each other and left roses at the memorial. Some held up placards with images of their loved ones who were killed.
President Donald Trump and First Lady Melania Trump welcomed victims' families and survivors to the White House where they marked the anniversary with a moment of silence.
Speaking at a ceremony marking the 18th anniversary of the 9/11 attacks, Trump said that over "the last four days" US forces have "hit our enemy harder than they have ever been hit before and that will continue."