On April 14, Joe Biden told Americans when their country's longest war would finally end:

"I'm now the fourth US president to preside over American troop presence in Afghanistan: two Republicans, two Democrats. I will not pass this responsibility on to a fifth."

Biden delivered his address in the White House Treaty Room. It was in this same room that George W. Bush had announced the US-led attack on Afghanistan on October 7, 2001:

"On my orders, the United States military has begun strikes against al Qaeda terrorist training camps and military installations of the Taliban regime in Afghanistan. These carefully targeted actions are designed to disrupt the use of Afghanistan as a terrorist base of operations, and to attack the military capability of the Taliban regime."

Between these two statements lie 20 years of war and terror.

Why did the US and its allies attack Afghanistan?

The beginning was driven by retaliation. The US had determined that Osama bin Laden and his al-Qaida network were responsible for the September 11, 2001, attacks in New York and Washington, DC, which killed 2,977 people.

Bin Laden had been running al-Qaida from Afghanistan since the fundamentalist Taliban seized power in 1996.

Just one day after the attacks, for the first time the NATO alliance invoked its mutual defense clause, according to which an attack on one member can be seen as an attack on all. On the same day, the United Nations Security Council adopted Resolution 1368, condemning the terrorist attacks and reaffirming the right to individual or collective self-defense.

On October 7, 2001, the United States and United Kingdom conducted their first airstrikes in Afghanistan.

Why did US-led NATO forces stay in the country for two decades?

The primary US goal was to hunt down Osama bin Laden and al-Qaida. But there was never a clear exit strategy. 

The troops stayed when the US launched another war, in Iraq in 2003. They also stayed after US special forces had killed Osama bin Laden on May 2, 2011 — albeit that operation happened not in Afghanistan, but in neighboring Pakistan, where he had apparently lived for at least five years.

"We delivered justice to bin Laden a decade ago, and we've stayed in Afghanistan for a decade since. Since then, our reasons for remaining in Afghanistan are becoming increasingly unclear, even as the terrorist threat we went to fight evolved," Biden said on April 14 in the Treaty Room.

"American troops shouldn't be used as a bargaining chip between warring parties in other countries," the president added. 

The decision to pull out is also an admission of failure. In fact, US and NATO forces were sucked ever deeper into power dynamics that they had created themselves: To eliminate al-Qaida in Afghanistan, the Western coalition had partnered with warlords such as Mohammed Fahim and Abdul Rashid Dostum, who have been accused of atrocities. Both men were appointed to terms as vice president during the decades that the US and NATO have been in Afghanistan.

Afghanistan had already experienced more than two decades of continuous war before US jets dropped their first bombs in 2001. From 1979 to 1989, the occupying Soviet forces battled loosely allied US-backed resistance fighters, many of whom would seek competing fates for Afghanistan when the Kremlin pulled out its troops, giving way to the still-unresolved civil war.

The warlords' brutal struggle with one another destroyed the capital, Kabul, and led to the Taliban's seizing of power.

Despite this complex history off alliances, the Taliban's opponents were perceived to be NATO's partners. The West invested billions of dollars into the goal of building a democratic Afghanistan after the Taliban's swift fall in December 2001. The US flatly refused to negotiate with officials from the toppled Islamist regime, many of whom fled toward Pakistan.

The seeds were sown for new violence, new terror and rampant corruption.

NATO's deployment grew over the years, eventually involving close to 50 nations. The mission, which had been pitched as one of reconstruction and peace, turned into a combat mission as the Taliban regrouped and rearmed to wage a full-blown insurgency.

Afghanistan expert Ibraheem Bahiss, who also advises the International Crisis Group, sums it up in one sentence: "Once you have overthrown a force that was ruling over the country and replaced it with a disparate group of actors with diverging priorities and capabilities, it seems like there really is very little choice other than to engage in some ways to keep the country from falling apart."

But, after two decades, the US has now decided that Afghanistan, even if it disintegrates, does not pose enough of a global threat to keep boots on the ground. US security interests are focused primarily on an increasingly assertive China.

How many victims have died in this war?

According to the UN Assistance Mission to Afghanistan, which has documented the number of civilian casualties since 2009, nearly 111,000 civilians had been killed or injured by the end of 2020. The Taliban and other extremist groups are responsible for most of the casualties. But international troops have also killed many innocent civilians — especially when attacking villages with fighter jets and drones. 

The US Army has lost 2,442 soldiers; the Bundeswehr, 59. It is unknown how many Afghan soldiers and police officers have been killed. That devastating figure has been kept secret for many years out of security concerns. In January 2019, however, President Ashraf Ghani made the surprise announcement at the World Economic Forum in Davos that more than 45,000 members of the Afghan security forces had lost their lives since he took office in 2014.

There is also no reliable information on the number of Taliban fighters and other extremists killed in the conflict. According to calculations by the Costs of War Project at the prestigious Brown University in Rhode Island and judging by current media reports, a figure considerably higher than 50,000 seems very realistic.

What is known about the cost of the war?

Brown University's Costs of War Project has also estimated that the United States spent more than $2 trillion (€1.7 trillion) on the war in Afghanistan from October 2001 through April 2021. About half of this sum, $933 billion, was spent on the US Army. According to the White House, the US invested $144 billion in the reconstruction of Afghanistan during the same period. The bulk of this sum, more than $88 billion, went toward the Afghan security forces.

Government sources indicated to DW that Germany spent more than €18 billion on the Afghanistan intervention from 2002 through 2020. According to the Defense Ministry, by far the largest share, €12.5 billion, was spent on the Bundeswehr mission.

The German Foreign Ministry has provided civilian support amounting to €2.4 billion since 2001, a spokeswoman told DW. The building of state institutions was supported with about €950 million from 2002 through 2019, she said.

What has the international intervention achieved and where has it failed?

When the intervention began in October 2001, Afghanistan was an isolated, devastated country where women were stoned to death and political opponents executed. Only three countries recognized the Taliban's fundamentalist emirate: Pakistan, Saudi Arabia and the United Arab Emirates.

Today, Afghanistan is an Islamic republic with a Western-sponsored democratic constitution and an internationally recognized, elected government. Women sit in parliament, and girls attend school. "There is greater public knowledge about human rights, and a more vibrant discourse around human rights across Afghanistan," Shaharzad Akbar, the chairwoman of the Afghan Independent Human Rights Commission, told DW. She said that was a massive achievement.

Younger Afghans have benefited greatly from new schools and universities and continue to display an incredible thirst for education. Access to health care has increased, as has the number of roads, cellphone towers, dams, bridges, power pylons and water pipes. But the country has not found peace and has deep social and economic divisions, as much of the aid has only reached the urban elites.

More than half of the population continues to live in abject poverty. The contested areas in the south and east of the country — the heartland of the Taliban — are in particularly bad shape after bearing the brunt of Western firepower and then being left behind by the reconstruction effort.

UN Special Envoy Deborah Lyons fears that escalating violence and the coronavirus pandemic could push the poverty rate from nearly 50% to over 70%. "I cannot stress enough my concern about the current situation in Afghanistan," she told the UN Security Council on June 22.

Meanwhile, US intelligence agencies have concluded that the government could collapse within six months of the departure of the last international troops. The possible "slide toward some dire scenarios is undeniable," Lyons said in her video conference with the Security Council.

Is there a chance for peace?

Not anytime soon. After the regime disintegrated in the winter of 2001, the Taliban were in a position of weakness, but the US categorically rejected talks. This attitude has backfired, because today the group projects itself as the winner of its war against mighty NATO — especially since the signing of the Doha Agreement with the US in February 2020. With Pakistani support, the Taliban have achieved one of their main goals: the unconditional withdrawal of international troops.

Ignoring calls for a cease-fire or at least a reduction in violence, they are now on the offensive and advancing on urban centers. The Taliban reject the Afghan constitution and want to replace it with a "truly Islamic system."

They have so far refused to share what this means exactly. The intra-Afghan peace talks, which began in the Qatari capital, Doha, in September 2020, have all but stalled.

In the first three months of this year, the number of civilian casualties increased dramatically. Women make up a large number of those killed in a deadly campaign of targeted attacks on media workers, judges and civil society activists.

"This escalation of violence means the Taliban are fighting to win," Human Rights Commissioner Akbar said. "They are fighting for a military takeover. They will resort to any means they think will help. "

If the radical Islamists do in fact seize power militarily, Afghanistan analyst Bahiss fears a return to the isolation of the 1990s: "It will be a pariah state with which the neighbors, including China, will only negotiate when and if they have to. Aid will dissipate. Pockets of resistance will continue."

What lessons should Western democracies learn?

At the beginning of President Barack Obama's tenure, the United States had briefly deployed about 100,000 troops in Afghanistan. But "wars are not won simply because you throw more men and more money at the problem," Bahiss said. That's why the US finally entered official negotiations with the Taliban in July 2018 — without involving the elected Afghan government or NATO partners.

"We went to Afghanistan because of a horrific attack that happened 20 years ago. That cannot explain why we should remain there in 2021," Biden said in the Treaty Room — in fact admitting that state-building by military means is not possible.

"War in Afghanistan was never meant to be a multi-generational undertaking," he said. "We were attacked. We went to war with clear goals. We achieved those objectives. Bin Laden is dead, and al Qaeda is degraded in Iraq, in Afghanistan. And it's time to end the forever war." 

Bahiss said Western democracies should "try a bit of humility and learn more about the societies they plan to transform." He said Afghanistan was a particular example of how wrong it is "to see everything as a military problem."

Akbar said a major issue was the lack of justice and accountability within NATO in Afghanistan. "The very fact that there was never a proper investigation into the credible allegations of abuse by international forces didn't help the credibility of international partners," she said. "Also, the fact that they worked with and empowered people despite the fact that there were credible allegations of war crimes against them in Afghanistan, didn't help them either."

As is the case with the conflict in Iraq, the war in Afghanistan has created more terror, not less. Al-Qaida's presence in the country is diminished, but the threat has metastasized elsewhere. The so-called Islamic State has emerged on the Afghan battlefield, too.

The war has roiled a volatile region in which nuclear powers India and Pakistan are locked in a hostile stand-off while Iran, China and Russia are seeking greater influence, too.

Afghanistan continues to be one of the three countries from which most refugees in Germany originate.